Heating element for an exhaust gas line
By designing multiple heating plates and providing mechanical support and electrical connections with connector devices, the problem of low heating efficiency of the exhaust line heating element during the initial stage of engine startup is solved, and a more efficient NOx removal reaction is achieved.
Patent Information
- Application Number
- CN202411424636.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-10-18
- Filing Date
- 2024-10-12
- Publication Date
- 2025-04-18
AI Technical Summary
The existing exhaust line heating elements are difficult to effectively heat the catalytic converter during the initial stage of engine startup, which affects the efficiency of NOx removal reaction.
An exhaust line heating element including at least two heating disks is designed to provide mechanical support and electrical connections through a connector device to ensure that exhaust gas passes through multiple heating disks and to heat the heating disk evenly by optimizing the electrical connection path.
Through the coordinated work of multiple heating plates, the initial heating efficiency of the exhaust gas and catalytic converter is improved, and the starting capability of the NOx removal reaction is enhanced.
Smart Images
Figure CN119854979A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a heating element for an exhaust gas line. Such a heating element is usually of the electrically heated type, also known as an EHC (Electrically Heated Catalyst). Prior art
[0002] Such heating elements are usually used to purify the exhaust gases that circulate in the exhaust line and are produced by combustion in the engine. Nitrogen oxides (NOx) are polluting compounds produced by the combustion of hydrocarbons and are usually removed by catalytic reduction reactions. This reaction requires a catalyst, which includes precious metals. The hot catalytic converter converts the NOx contained in the exhaust gases into non-polluting nitrogen N2 and water H20 by adding a reducing fluid, usually an aqueous solution of urea.
[0003] For the reduction reaction to be effective, the temperature of the catalyst must be very high. This is ensured in steady-state operation, as the catalytic converter is heated by the hot exhaust gases from combustion. However, this is not the case in the initial phase after the engine is started.
[0004] It is also known to place, in the exhaust line upstream of the catalytic converter, a heating element capable of heating the exhaust gases passing therethrough so as to heat the catalytic converter itself at the same time.
[0005] One possible design principle for such a heating element is to use a heating disk with holes in it through which the exhaust gases can pass. The heating disk is arranged in the flow section of the exhaust line. The heating disk is heated and is able to heat the exhaust gases as they pass through it.
[0006] In one possible embodiment, heating is achieved by applying an electric current between two ends of a metal heating disk to heat the heating disk using the Joule effect.
[0007] Recently it has been discovered that heating elements with more than one heating disk can be produced in sequence by fluid and electrical means in terms of performance and durability. This raises the question of the mechanical support of the heating disks and their electrical connection.
[0008] The present invention provides several embodiments for optimizing mechanical support and electrical connection. Summary of the invention
[0009] The present invention provides an exhaust line heating element, which includes a substantially tubular shell, which defines a channel portion for exhaust gas, and at least two heating disks contained in the shell are arranged in the channel portion to force the exhaust gas to pass through the at least two heating disks, wherein the heating element also includes a connector device, which supports the at least two disks and provides an electrical connection between the at least two disks.
[0010] Specific features or embodiments that may be used alone or in combination are:
[0011] - the connector device comprises a first wheel flange and a central electrode, the first wheel flange comprising: a rim substantially conforming to the periphery of the cross section of the exhaust gas passage; a hub adapted to support the central electrode; and spokes connecting the rim to the hub, the central electrode being electrically connected to the respective centers of the at least two disks,
[0012] - the rim of the first wheel flange has an L-shaped cross section, one arm of which is arranged radially and the other arm is arranged axially, the radial arm of the L-shaped cross section forming a first bearing surface capable of axially bearing against the periphery of a first disk of the at least two disks,
[0013] - the first wheel flange is arranged on the outside of at least two disks, with the radial arms of the L-shaped cross section abutting against the adjacent disks and the axial arms of the L-shaped cross section facing outwards,
[0014] - The first wheel flange is welded to the adjacent disc,
[0015] - a first insulating rim is arranged axially between said at least two disks, the hub being electrically insulated relative to the central electrode,
[0016] - the first wheel flange is arranged between the at least two disks, with the radial arm of the L-shaped cross section against the first disk and the axial arm of the L-shaped cross section towards the second disk,
[0017] - the first wheel flange is electrically insulated from the first disc by a second insulating rim axially inserted between the two,
[0018] - The first wheel flange is electrically insulated radially from the housing by a first peripheral gasket,
[0019] - the connector device further comprises a single flange comprising a rim having an L-shaped cross section which is inverted relative to the cross section of the rim of the first flange to form a second bearing surface which is capable of bearing against the periphery of a second disk of the at least two disks and is electrically insulated from the second disk by a third insulating rim axially interposed therebetween,
[0020] - The single flange is electrically insulated radially from the housing by a second peripheral gasket,
[0021] - the connector device comprises a first wheel flange and a second wheel flange, the first wheel flange and the second wheel flange being mounted end to end between two of the at least two disks electrically connected to each other, the wheel flange comprising: a rim substantially conforming to the periphery of the cross section of the exhaust gas passage; a hub; and spokes connecting the rim to the hub, the hub being electrically connected to the corresponding center of the adjacent disk, the rim being electrically insulated from the adjacent disk by an insulating rim axially inserted therebetween,
[0022] - the connector device comprises a cylindrical sheet consisting of a metal foam, arranged between a first and a second of the at least two disks, electrically connected to a first center of the first disk and to a second center of the second disk, axially electrically insulated from the remainder of the first disk by a second insulating rim, and axially electrically insulated from the remainder of the second disk by a third insulating rim, the metal foam being preferentially coated to produce a catalytic effect,
[0023] - for each of said at least two disks, the heating element further comprises a peripheral electrode electrically connected to the periphery of said disk,
[0024] - The wheel well also includes a mixing device,
[0025] - the connector means comprises a substantially tubular connector, the interior of which conforms to the shape of the housing so as to provide an electrical connection between the respective peripheries of said at least two discs,
[0026] - for each of the at least two disks, the heating element further comprises a central electrode which is electrically connected from the outside to the center of the disk, respectively,
[0027] - The connector device further comprises a catalytic brick arranged between said at least two disks. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The invention will be better understood by reading the following description, which is given by way of example only, and by referring to the accompanying drawings, in which:
[0029] [ Figure 1 ] shows a cross-sectional view of a heating element according to a first embodiment along its axis,
[0030] [ Figure 2 ] shows [ Figure 1 ] a perspective view of a heating element shown in FIG.
[0031] [ Figure 3 ] shows a cross-sectional view of a heating element according to a second embodiment along its axis,
[0032] [ Figure 4 ] shows [ Figure 3 ] a perspective view of a heating element shown in FIG.
[0033] [ Figure 5 ] shows a cross-sectional view of a heating element according to a third embodiment along its axis,
[0034] [ Figure 6 ] shows [ Figure 5 ] a perspective view of a heating element shown in FIG.
[0035] [ Figure 7 ] shows a cross-sectional view of a heating element along its axis according to a variant of the third embodiment,
[0036] [ Figure 8 ] shows [ Figure 7 ] a perspective view of a heating element,
[0037] [ Fig. 9 ] shows a cross-sectional view of a heating element along its axis in a fourth embodiment,
[0038] [ Fig.10 ] shows [ Fig. 9 ] a perspective view of a heating element,
[0039] [ Fig.11 ] shows a cross-sectional view of a heating element according to a fifth embodiment along its axis,
[0040] [ Fig.12 ] shows [ Fig.11 ]A perspective view of the heating element in FIG.
[0041] Reference numerals list
[0042] 1: heating element, 2: shell, 3, 4: heating plate, 5, 6: center, 8: first wheel flange, 9: rim, 10: hub, 11: spokes, 12: center electrode, 13: first supporting surface, 14: first insulating rim, 15: second insulating rim, 16: third insulating rim, 17: first radial insulating pad, 18: second radial insulating pad, 19: single flange, 20: second supporting surface, 21: second wheel flange, 22: rim, 23: hub, 24: spokes, 25: cylindrical sheet, 26, 27: peripheral electrodes, 28: connector, 29, 30: center electrode, 31: catalytic brick, 32: radial insulating pads, 33, 34: single flange. DETAILED DESCRIPTION
[0043] In this document, the terms "radial" and "axial" are used in relation to the axis of the exhaust line or housing. The term "axial" means that the element is substantially aligned with said axis, while "radial" means that the element is substantially perpendicular to said axis.
[0044] The invention relates to a heating element 1 for an exhaust gas line. The heating element 1 comprises a substantially tubular housing 2 which is integral with or forms a part of the exhaust gas line and defines a passage section for the exhaust gas. The housing 2 accommodates at least two heating discs 3, 4 arranged in the passage section to force the exhaust gas to pass through the at least two heating discs 3, 4.
[0045] According to another feature, the heating element 1 further comprises a protective cover. The connector has two functions: mechanical support and electrical connection. The connector means provide mechanical support for the at least two discs 3, 4. The connector means also provide an electrical connection between the at least two discs 3, 4.
[0046] For heating purposes, the disks 3, 4 must be electrically connected at two points, preferably at the ends, so that the current flows as evenly as possible over the entire surface of the at least two disks 3, 4. According to the features used here, a first point is located at the center 5, 6 of the disks 3, 4 and another point is located at the periphery of the disks 3, 4. This ensures that the current flows radially and substantially evenly between these two points.
[0047] The two disks 3 , 4 are advantageously electrically connected in series.
[0048] Several embodiments of the connector and support arrangement are contemplated.
[0049] According to the features used in several embodiments, more specifically in Figures 1 to 4 , the connector device comprises a first wheel flange 8 and a center electrode 12.
[0050] The first wheel flange 8 is wheel-shaped. The first wheel flange comprises: a rim 9, which is substantially conformed to the periphery of the exhaust gas passage portion; a hub 10, preferably located in the center; and spokes 11, which connect the rim 9 to the hub 10. The hub 10 accommodates and fixes a center electrode 12. The center electrode 12 provides an electrical connection between the center 5 of the first disk 3 and the center 6 of the second disk 4.
[0051] The wheel flange 8 is preferably made of metal and is stamped. This allows the production of low-cost components and control of their manufacture and supply. Therefore, the wheel flange 8 is electrically conductive. In order to avoid short circuits, appropriate electrical insulation must be installed.
[0052] According to another feature, the rim 9 of the first wheel flange 8 has an L-shaped cross section. One arm of the L-shaped cross section is arranged radially. The other arm of the L-shaped cross section is arranged axially. The radial arm of the L-shaped cross section thus forms a first bearing surface 13. This first bearing surface is thus able to bear axially against the periphery of the first disk 3 of the at least two disks 3, 4.
[0053] According to the first embodiment, more specifically, Figure 1 and Figure 2 As shown, the heating element 1 comprises a first wheel flange 8 arranged outside the at least two disks 3, 4. The radial arm of the L-shaped cross section abuts against a disk 3, which is called the adjacent disk 3. The axial arm of the L-shaped cross section faces outward from the at least two disks 3, 4.
[0054] According to another feature of the first embodiment, the first wheel flange 8 is directly welded to the adjacent disk 3. This ensures the mechanical reinforcement provided by the first wheel flange 8, which can reinforce and further support the adjacent disk 3. The first wheel flange 8 is preferably made of a metal material and participates in the circuit and electrical connection between the at least two disks 3, 4.
[0055] In order to avoid short circuits, at least two disks 3, 4 must be electrically insulated at carefully selected points. To this end, according to another feature of the first embodiment, a first insulating rim 14 is axially arranged between the at least two disks 3, 4. This first insulating rim 14 is a peripheral component and covers at least the respective periphery of the disks 3, 4. In addition, in order to complete the electrical insulation diagram and define the current flow path, the hub 10 is electrically insulated relative to the center electrode 12. This first insulating rim 14 is made of a cord (usually fiberglass), for example.
[0056] According to another feature previously described, each of the disks 3 , 4 comprises a peripheral electrode 26 , 27 respectively connecting the periphery of the disk 3 , 4 .
[0057] Furthermore, the circuit of this first embodiment enters via the first peripheral electrode 26, passes through the periphery of the first disk 3, radially passes through the first disk 3 to its center 5, then passes through the center electrode 12 to the center 6 of the second disk 4, radially passes through the second disk 3 from its center 6 to its periphery, and exits via the second peripheral electrode 27 connected to the periphery. A current generator connected between the two peripheral electrodes 26, 27 circulates current and heats the two disks 3, 4.
[0058] According to a second embodiment, more specifically Figure 3 and Figure 4 As shown, the first wheel flange 8 is arranged between the at least two disks 3, 4. In this case, the radial arm of the L-shaped cross section abuts against the first disk 3 and the axial arm of the L-shaped cross section faces the second disk 4.
[0059] To avoid short circuiting through the first wheel flange 8, according to another feature of the second embodiment, the first wheel flange 8 and the first disc 3 are electrically insulated by a second insulating rim 15 axially inserted therebetween. The second insulating rim 15 is made of cord (usually fiberglass), for example.
[0060] According to another feature of the second embodiment, the first wheel flange 8 is electrically insulated radially from the housing 2 by a first radial insulating mat 17. The radial insulating mat 17 is usually a glass fiber mat, also called a cladding mat.
[0061] According to another feature of the second embodiment, the connector device further comprises a single flange 19. The single flange 19 looks like a wheel flange, but without a central portion. The single flange 19 further comprises a rim similar to the rim 9. The rim has an L-shaped cross section. The cross section is inverted relative to the cross section of the rim 9 of the first wheel flange 8. Thus, the radial L arm forms a second bearing surface 20, which is able to bear against the periphery of the second disk 4 of the at least two disks 3, 4. The single flange 19 is electrically insulated from the second disk 4 by a third insulating rim 16 axially inserted therebetween. The third insulating rim 16 is made, for example, of cord (usually fiberglass).
[0062] According to another feature of the second embodiment, the single flange 19 is electrically insulated radially from the housing 2 by a first radial insulating mat 17. The radial insulating mat 17 is usually a glass fiber mat, also called a cladding mat.
[0063] In this second design, no electrical insulation is required between the first wheel flange 8 at its hub 10 and the central electrode 12 carried by said hub 10 , due to the insulation provided by the first radial insulating spacers 17 .
[0064] Furthermore, for this second embodiment, the electrical circuit enters via the first peripheral electrode 26, passes through the periphery of the first disk 3, crosses through the first disk 3 to its center 5, then passes through the center electrode 12 to the second disk 4, crosses through the second disk 4 to its periphery, and exits via the second peripheral electrode 27. The current generator connected between the two peripheral electrodes 26, 27 circulates current and heats the two disks 3, 4.
[0065] According to a third embodiment, in particular Figures 5 to 8 As shown, the connector device comprises two substantially identical wheel flanges 8, 21. The first wheel flange 8 and the second wheel flange 21 are arranged end to end between two of the at least two disks 3, 4. The two wheel flanges 8, 21 are electrically connected to each other. This connection is achieved by bringing the wheel rims 9, 22 into contact with each other, which may also be supplemented by welding. This contact is achieved via the corresponding bearing surfaces 13, 20.
[0066] Similar to the first wheel flange 8 , the second wheel flange 21 includes a rim 22 that substantially conforms to the periphery of the exhaust passage, a hub 23 , and spokes 24 that connect the rim 22 to the hub 23 .
[0067] Each of the wheel flanges 8, 21 is electrically connected to the respective disc 3, 4 via a hub 10, 23. The hubs 10, 23 are electrically connected to the respective centers 5, 6 of the adjacent discs 3,4.
[0068] This is supplemented by electrically insulating each of the rims 9, 22 by axially inserted insulating rims 15, 16. These insulating rims 15, 16 are made, for example, of cords, typically fiberglass.
[0069] This is supplemented by the radial electrical insulation provided by the second radial insulating pads 18 , which are radially arranged between the rims 9 , 22 and the single flanges 33 , 34 , which are respectively in electrical contact at the periphery with each of the disks 3 , 4 , the single flanges 33 , 34 themselves being electrically insulated by the first radial insulating pads 17 .
[0070] Furthermore, the electrical circuit of this third embodiment enters the periphery of the first disk 3 via the first peripheral electrode 26, passes through the first disk 3 to its center 5, then passes through the first wheel flange 8 via its hub 10, via its spokes 11 to its rim 9. The two rims 9, 22 are in contact and ensure electrical connection between the two wheel flanges 8, 21. The current then reaches the second wheel flange 21, through the second wheel disk 21, via its spokes 24 to its hub 23. This hub 23 is connected to the center 6 of the second disk 4. The current then flows through the second disk 4 to its periphery and out via the second peripheral electrode 27. The current generator connected between the two peripheral electrodes 26, 27 circulates the current and heats the two disks 3, 4.
[0071] Figure 7 and Figure 8 A variation of the third embodiment is shown. In the third embodiment, the single flanges 33, 34, respectively associated with each of the disks 3, 4, are arranged with the radial arms of the L-shaped cross section facing outwards. In an alternative embodiment, the single flanges 33, 34 are arranged with the radial arms of the L-shaped cross section facing inwards. Furthermore, in this variation, the peripheral electrodes 26, 27 are arranged substantially in the same plane perpendicular to the axis. These two features make the heating element 1 more compact in the axial direction.
[0072] In a fourth embodiment, the connector device comprises a cylindrical sheet 25 consisting of a metal foam. The cylindrical sheet 25 is arranged between the first disk 3 and the second disk 4 of the at least two disks 3, 4. The cylindrical sheet is electrically connected to the first center 5 of the first disk 3 and the second center 6 of the second disk 4. Therefore, in the previous two embodiments, the cylindrical sheet acts as the center electrode 12. On the other hand, the cylindrical sheet is axially electrically insulated from the rest of the first disk 3 by the second insulating rim 15, and is axially electrically insulated from the rest of the second disk 4 by the third insulating rim 16. As a preferred option, the metal foam can be coated with a catalytic material to produce a catalytic effect.
[0073] Furthermore, for this fourth embodiment, the electrical circuit enters via the first peripheral electrode 26, passes through the periphery of the first disk 3, crosses the first disk 3 laterally to its center 5, and then reaches the center 6 of the second disk 4 via the cylindrical sheet 25 composed of metal foam. The current then flows through the second disk 4 to its periphery and exits via the second peripheral electrode 27. The current generator connected between the two peripheral electrodes 26, 27 circulates the current and heats the two disks 3, 4.
[0074] According to another feature common to the first, second, third and fourth embodiments, the heating element 1 further comprises, for each of said at least two disks 3 , 4 , a peripheral electrode 26 , 27 electrically connected to the periphery of said disks 3 , 4 .
[0075] To achieve an electrical connection between the electrodes 26, 27 and the associated disks 3, 4, the disks 3, 4 are advantageously arranged in a single flange 33, 34. This single flange 33, 34 has an L-shaped profile, similar to the single flange 19 already described in the second embodiment. Such a single flange 33, 34 can provide an axial bearing surface for the disks 3, 4 via radial L-shaped arms. For example, this bearing surface can make the disks 3, 4 rest against the insulating rims 15, 16.
[0076] According to another feature, and according to one of the first, second or third embodiments, the heating element 1 may comprise at least one wheel flange 8, 21 comprising mixing means. The mixing means may be obtained, for example, by shaping the spokes 11, 24 in the shape of fins. These fins may thus deflect the exhaust gas flow towards a more specific area of the heating disk 3, 4 located downstream of the wheel flange 8, 21 or at a given angle of incidence. Thus, the mixing means may deflect the exhaust gases so that they reach the surface of the heating disk 3, 4 with oblique incidence.
[0077] According to the fifth embodiment, more specifically as Fig.11 and Fig.12 As shown, the connector device comprises a substantially tubular connector 28, which matches the shape of the housing 2 from the inside. The connector 28 is electrically conductive and has a shape that ensures electrical connection with the periphery of the first plate 3 on the one hand and with the periphery of the second plate 4 on the other hand. Here, the connection between the heating plates 3, 4 is achieved by making contact between their peripheries, rather than by making contact between their centers 5, 6 as in the previous embodiment.
[0078] For this purpose, the connector 28 must be insulated from the housing 2, for example, by a radial insulating mat 17 radially arranged between the connector 28 and the housing 2. The radial insulating mat 17 is usually a glass fiber mat, also called a cladding mat.
[0079] Since the two disks 3, 4 are connected at their peripheries, the current must flow in and out through their respective centers 5, 6. To this end, according to another feature, the heating element 1 also comprises a central electrode 29, 30 of each heating disk 3, 4. Each of these central electrodes 29, 30 is electrically connected to the center 5, 6 of its associated disk 3, 4, respectively. Advantageously, this connection is made from the outside of the disk assembly 3, 4, so that the central electrodes 29, 30 are easily accessible to the disks 3, 4.
[0080] We have seen that the connector 28 is cylindrical and advantageously hollow. The space between the heating plates 3 and 4 is also empty. According to another feature of the connector device, it comprises a catalytic brick 31 arranged between the plates 3, 4. The catalytic brick 31 thus exploits the free space while improving pollution control.
[0081] The invention has been described and illustrated in detail in the drawings and the foregoing description. This must be considered as illustrative and given by way of example, rather than limiting the invention to this description alone. Many alternative embodiments may be employed.
Claims
1. A heating element (1) for an exhaust gas line, comprising a substantially tubular housing (2), the housing defining a passage portion for the exhaust gases, the housing containing at least two heating discs (3, 4) arranged in the passage portion to force the exhaust gases to pass through the at least two discs (3, 4), characterized in that The heating element (1) further comprises connector means, which support the at least two discs (3, 4) and provide an electrical connection between the at least two discs (3, 4).
2. The heating element (1) according to claim 1, wherein the connector device comprises a first wheel flange (8) and a central electrode (12), the first wheel flange (8) comprising: a rim (9) substantially conforming to the periphery of the passage portion of the exhaust gas; A hub (10) capable of supporting the central electrode (12); and spokes (11) connecting the rim (9) to the hub (10), the central electrode (12) being electrically connected to the respective centers (5, 6) of the at least two disks (3, 4).
3. The heating element (1) according to claim 2, wherein the rim (9) of the first wheel flange (8) has an L-shaped cross-section, one arm of the L-shaped cross-section is arranged radially, and the other arm of the L-shaped cross-section is arranged axially, and the radial arm of the L-shaped cross-section forms a first bearing surface (13), which can axially abut against the periphery of the first disk (3) of the at least two disks (3, 4).
4. A heating element (1) according to any one of claims 2 or 3, wherein the first wheel flange (8) is arranged on the outside of the at least two disks (3, 4), the radial arms of the L-shaped cross section abut against the adjacent disk (3), and the axial arms of the L-shaped cross section face outward.
5. The heating element (1) according to claim 4, wherein the first wheel flange (8) is welded to the adjacent disk (3).
6. A heating element (1) according to any one of claims 4 or claim 5, wherein a first insulating rim (14) is arranged axially between the at least two disks (3, 4), and wherein the hub (10) is electrically insulated relative to the central electrode (12).
7. A heating element (1) according to any one of claims 2 or 3, wherein the first wheel flange (8) is arranged between the at least two disks (3, 4), the radial arm of the L-shaped cross section abuts against the first disk (3), and the axial arm of the L-shaped cross section faces the second disk (4).
8. The heating element (1) according to claim 7, wherein the first wheel flange (8) is electrically insulated from the first disk (3) by an axially inserted second insulating rim (15).
9. The heating element (1) according to any one of claims 7 or 8, wherein the first wheel flange (8) is radially electrically insulated from the housing (2) by a first radial insulating gasket (17).
10. A heating element (1) according to any one of claims 7 to 9, wherein the connector device further comprises a single flange (19), the single flange comprising a rim having an L-shaped cross section, the L-shaped cross section being inverted relative to the cross section of the rim (9) of the first wheel flange (8) to form a second bearing surface (20), the second bearing surface being capable of abutting against the periphery of the second disk (4) of the at least two disks (3, 4) and being electrically insulated from the second disk (4) by a third insulating rim (16) axially inserted therebetween.
11. The heating element (1) according to claim 10, wherein the single flange (19) is radially electrically insulated from the housing (2) by the first radial insulating gasket (17).
12. A heating element (1) according to claim 1, wherein said connector means comprises a first wheel flange (8) and a second wheel flange (21), said first wheel flange and said second wheel flange being mounted end to end between two of said at least two discs (3, 4) being electrically connected to each other, one wheel flange (8, 21) comprising: a rim (9, 22) substantially conforming to the periphery of the passage portion of the exhaust gas; Hub(10,23); and spokes (11, 24) connecting the rims (9, 22) to the hubs (10, 23), one hub (10, 23) being electrically connected to the respective centers (5, 6) of the adjacent disks (3, 4), and one rim (9, 22) being electrically insulated from the adjacent disks (3, 4) by an insulating rim (15, 16) axially interposed therebetween.
13. A heating element (1) according to claim 1, wherein the connector device comprises a cylindrical sheet (25) composed of metal foam, which is arranged between the first disk (3) and the second disk (4) of the at least two disks (3, 4), is electrically connected to the first center (5) of the first disk (3) and the second center (6) of the second disk (4), is axially electrically insulated from the rest of the first disk (3) by a second insulating rim (15), and is axially electrically insulated from the rest of the second disk (4) by a third insulating rim (16), and the metal foam is preferentially coated to produce a catalytic effect.
14. A heating element (1) according to any one of claims 2 to 12, wherein the wheel well (8, 21) further comprises a mixing device.
15. A heating element (1) according to claim 1, wherein the connector means comprises a substantially tubular connector (28), the interior of which conforms to the shape of the housing (2) so as to provide an electrical connection between the respective peripheries of the at least two discs (3, 4).
16. The heating element (1) according to claim 15, further comprising, for each of the at least two disks (3, 4), a central electrode (29, 30) electrically connected from the outside to the center (5, 6) of the disk (3, 4), respectively.
17. A heating element (1) according to any one of claims 15 or 16, wherein the connector arrangement further comprises a catalytic brick (31) arranged between the at least two discs (3, 4).