Device for an electrically heatable honeycomb body

Abstract

A device (1) at least comprising a casing (2) with an inner side (3) which surrounds a flow channel (4), further comprising a honeycomb body (5) which is positioned in the flow channel (4) at a spacing from the inner side (3), such that a gap (6) is formed between the inner side (3) and the honeycomb body (5), wherein the honeycomb body (5) is electrically conductive, and at least one current distributing element (7) partially surrounds the honeycomb body (5), the device (1) further comprising at least one electrode bushing (8) through the casing (2), wherein at least one electrode (9) extends through the electrode bushing (8) to the at least one current distributing element (7), and the at least one current distributing element (7) is mounted at a spacing from the electrode bushing (8) by means of at least one fastening element (10) in an enclosure (11) which is positioned outside the gap (6).

Description

[0001] Device for an electrically heated honeycomb body

[0002] The invention relates to a device for an electrically heatable honeycomb body, which is particularly suitable for exhaust gas aftertreatment of internal combustion engines.

[0003] The invention particularly relates to a device having at least one casing (as a housing) with an inner surface that surrounds or forms a flow channel. A honeycomb body is positioned in the flow channel. The purification of an exhaust gas stream in a catalytically loaded carrier layer of a catalyst carrier body, in particular in a motor vehicle exhaust system, takes place in a preferred temperature range. In order to achieve this temperature range even during cold start phases, electrical heating of the exhaust gas stream is carried out in certain scenarios. In a motor vehicle exhaust system, the device is used to heat the exhaust gas stream. The exhaust gas stream is passed through the honeycomb body, which is electrically contacted and can provide heating power. The exhaust gas stream is heated and then guided to the catalytically active carrier layer, where the exhaust gas stream is purified.

[0004] In some configurations, it may be useful to design the honeycomb with several resistor paths that can be powered separately or together, so that a predetermined heat output can be delivered as needed or evenly across the cross-section. If the honeycomb is made with metallic foils, the honeycomb can, for example, be made from several layer stacks (each consisting of a stack of alternating corrugated and less corrugated or smooth foils). The layer stacks can form intertwined or meandering paths.

[0005] Each electrically heatable path or track has two ends, each forming an electrical contact. At least one current distribution element can be used to connect these ends to an electrode through a casing in which the honeycomb body is arranged. The ends are connected to the at least one current distribution element at a distance from or adjacent to one another, or extend (fan-shaped) to an inner side of the casing and are connected there to the at least one current distribution element. An electrical feedthrough allows the electrode to penetrate the casing in an insulated and sealed manner, enabling electrical contact outside the casing to a voltage source.

[0006] The integration of such electrically heated honeycomb structures into a mobile exhaust system poses numerous challenges, particularly with regard to the device's durability despite high dynamic loads and / or intensive thermal cycling. These challenges become even more stringent as the honeycomb structure becomes more complex (with regard to current paths, contacts, insulation, etc.) and / or the honeycomb structure becomes larger.

[0007] Based on this, the object of the invention is to at least partially solve the problems described with reference to the prior art. In particular, it is intended to create a method by which an electrically heatable honeycomb body in the casing of an exhaust aftertreatment system can be further or effectively stabilized, in particular without (extensive) modifications to the exhaust system.

[0008] This object is achieved by the features of the independent claims. Further advantageous embodiments of the invention are specified in the dependent claims. It should be noted that features listed individually in the claims can be combined with one another in any technologically expedient manner and define further embodiments of the invention. Furthermore, the features listed in the claims are specified and explained in more detail in the description, with further preferred embodiments of the inventions being presented. A device which has a casing with an inner side that surrounds a flow channel contributes to the solution of this object. The device further has a honeycomb body positioned in the flow channel and at a distance from the inner side, such that a gap is formed between the inner side and the honeycomb body.The honeycomb body is electrically conductive, and at least one current distribution element partially surrounds the honeycomb body. The device further comprises at least one electrode feedthrough through the casing. At least one electrode extends through the electrode feedthrough to the at least one current distribution element. The at least one current distribution element is mounted at a distance from the electrode feedthrough by means of at least one fastening element in a frame positioned outside the gap.

[0009] The casing forms in particular a housing for the exhaust gas flow and can be designed, for example, in the manner of a hood, a pipe section, etc.

[0010] (At least) one honeycomb body is arranged inside the shell or in the flow channel for the exhaust gas formed thereby. The honeycomb body can be formed with a plurality of passages, microchannels, etc., through which the exhaust gas can flow through the honeycomb body (in a main flow direction).

[0011] The honeycomb body can be formed from ceramic and / or metallic material. The honeycomb body can partially, predominantly, or even substantially completely cover the flow channel and, in particular, be arranged at right angles to a longitudinal axis of the casing. The honeycomb body covers at least 90% or even at least 95% of the (inner) surface of the casing through which the fluid is to flow in the main flow direction.

[0012] The at least one honeycomb body is mounted at a distance from the shell in its interior, in particular to ensure electrical insulation of the honeycomb body and shell even under rapidly changing ambient conditions (pressure, temperature, vibration, etc.). For this purpose, an (annular) gap is provided in particular, surrounding the honeycomb body in the circumferential direction. The gap is in particular an annular region having an outer circumference and an inner circumference. The shape of the gap can be substantially round, oval, or the like, and is in particular adapted to the inner contour of the shell or the outer contour of the honeycomb body. The width of the gap is limited in a radial direction of the honeycomb body by an outer circumferential surface of the honeycomb body and the inner side of the shell. The height of the gap is limited in an axial direction of the honeycomb body by the height of the honeycomb body.The height of the gap thus corresponds to the height of the honeycomb body in the axial direction of the honeycomb body. The gap should be as small / narrow as possible (from a radial perspective), as this may allow a bypass flow past the honeycomb body, which could potentially negatively impact the efficiency of the honeycomb body or the exhaust gas heating device.

[0013] The at least one current distribution element can be arranged in the gap between the honeycomb body and the casing, viewed in a radial direction of the device. The current distribution element thus electrically contacts the honeycomb body in at least one predetermined (circumferential) region. The casing further has at least one electrode feedthrough (e.g. a gas-tight and possibly electrically insulated passage) through which at least one electrode extends. The end of the electrode protruding into the interior of the casing extends to a connection point on the at least one current distribution element. From there, the current distribution element preferably runs (practically only) in a circumferential direction and electrically contacts a honeycomb body region (also) in the circumferential direction at a distance from the electrode axis.Several electrode feedthroughs with associated electrodes and current distribution elements can be provided distributed around the circumference, so that electrical heating circuits or paths are formed in the honeycomb body (possibly also separately activatable or even separately controllable). It is possible for the electrodes to have (partial) different polarity (positive, negative). It is possible for several electrodes (electrically separated from one another) to penetrate the casing in one electrode feedthrough. The honeycomb body can be designed with at least two heating paths. Each track of such a heating path represents an electrical power path, which has one end with a positive contact and one end with a negative contact.

[0014] The tracks can be designed as a (separate) heating conductor in an (electrically non-conductive) honeycomb material.

[0015] The tracks can (preferably) be formed with (electrically insulated) stacks of metal foils, for example, comprising alternating corrugated and smooth (or less corrugated) metal foils, wherein the corrugations form channels for the exhaust gas to flow through, and the metal foils themselves can dissipate heat when electrical current flows through them. The tracks can be twisted within one another or run in a meandering pattern, whereby they are kept electrically insulated from one another by means of gaps and / or insulators. The ends of the tracks extend (fan-shaped) to the outer peripheral surface of the honeycomb body and terminate at least partially at a current distribution element.

[0016] The at least one current distribution element can be designed as a curved sheet metal element or one that follows the circumference of the honeycomb body, so that it may also correspond to a rounded shape of the annular region of the gap. The thickness of the current distribution element in the radial direction of the honeycomb body is less than the gap width in this direction. The at least one current distribution element therefore does not completely fill the annular region of the gap.

[0017] With at least two tracks or heating paths of the honeycomb body, a region can be created in which at least two ends of a track extend adjacently along the outer circumferential surface. The ends of the tracks thus extending can be connected to the electrode using the at least one current distribution element. The at least one current distribution element is designed in particular to conform to the at least two ends of a track and connect them.

[0018] The at least one current distribution element preferably extends exclusively in the gap between the honeycomb body and the casing. In the gap, the at least one current distribution element is (laterally) connected to the honeycomb body. In a honeycomb body with more than one track, the length of the at least one current distribution element can be extended accordingly from the connection to the electrical feedthrough in the circumferential direction of the honeycomb body.

[0019] In a honeycomb body with at least two or more tracks, the at least one current distribution element can have a considerable length in the circumferential direction, so that it is proposed here that, in addition to the connection to the electrode (at a first end), it is also held by at least one fastening element. The at least one fastening element can counteract undesirable or particularly severe bending or twisting of the at least one current distribution element.

[0020] The at least one fastening element is mounted in a frame positioned outside the gap. The at least one fastening element can be attached to the at least one current distribution element at one (first) end. Another (second) end of the at least one fastening element can protrude from the gap and be mounted or supported in a frame remote from the gap. The at least one fastening element can protrude from the gap in any (axial) direction.

[0021] It is possible for the at least one fastening element to be a rod-shaped element having a flat (first) end that is fastened to an outer surface of the at least one power distribution element. It is also possible for the at least one fastening element to be a rod-shaped element and have a cylindrical (first) end region. The at least one fastening element can rest against the outer surface of the at least one power distribution element in the cylindrical end region and be connected thereto.

[0022] A bezel can accommodate the other (second) end of the at least one fastening element so that it can be fastened therein. The bezel can be an annular or cylindrical receptacle into which the other end of the at least one fastening element is inserted. The receptacle can be designed as an open passage or a pocket that is closed (on one side). The bezel preferably encloses the (second) end of the fastening element or (comprehensively) accommodates it. The at least one fastening element can be fixed in the bezel with a material-to-material connection.

[0023] Preferably, a (single) enclosure is provided for each fastening element. However, it is possible for the fastening element to have multiple (second) ends, each of which is then provided with a separate enclosure.

[0024] The at least one power distribution element can be electrically insulated from the at least one fastening element. The fastening element is preferably designed with insulation, e.g., in the form of a coating or sleeve. Preferably, the fastening element is in contact with or attached to the power distribution element only via this (own) insulation.

[0025] The at least one current distribution element can have a cross-sectional area of ​​at least 10 mm 2 [square millimeters]. The minimum cross-sectional area is then preferably approximately 15 mm 2The cross-sectional area can be determined as the product of the width of the current distribution element in the radial direction of the honeycomb body and the height of the current distribution element in the axial direction of the honeycomb body. Such a minimum cross-sectional area ensures that a predetermined electrical current or a predetermined electrical current density is not exceeded. To ensure correct heat development in the honeycomb body, a minimum current strength is necessary. For current distribution elements with a cross-sectional area that is too small or too thin, a high electrical current or a high electrical current density would be necessary. The power of the minimum electrode can be limited to an electrical current of a maximum of 300 A [amperes] or a current density of 10 - 30 A / mm 2[amperes per square millimeter]. Power distribution elements that are too thin and have a high ohmic resistance could therefore lead to power losses in the honeycomb structure.

[0026] The at least one current distribution element can have a minimum cross-sectional area of ​​10 mm 2 Preferably, the minimum cross-sectional area is between 30 mm 2 and 45 mm 2 The minimum cross-sectional area can depend on the current flowing through the electrode bushing to the power distribution element. The electrode bushing can be powered by a motor vehicle's electrical system. If the electrical system has a voltage of 48 V [volts], for example, a power of approximately 14 kW [kilowatts] can be fed into the electrode bushing. This would result in a current of 300 A [amperes]. To accommodate such a current, the minimum cross-sectional area is preferably between 40 mm2 and 45 mm 2 Lower currents can also be fed in. On-board power systems typically have a power output of 10 kW, resulting in a current of 200 A. At this current, the minimum cross-sectional area would preferably be 30 mm 2 . When two tracks of the honeycomb body are connected to the current distribution element, the current can be distributed between the tracks.

[0027] The at least one power distribution element can have a maximum cross-sectional area of ​​80 mm 2 [square millimeters]. The maximum cross-sectional area is particularly preferably approximately 65 mm 2 , especially at approx. 50 mm 2If such a maximum cross-sectional area is exceeded, the at least one current distribution element may be too thick. Current distribution elements that are too thick have a higher inherent weight and may tend to bend under the influence. Current distribution elements that are too thick may also cause them to overfill the annular area between the honeycomb body and the casing. This could result in electrical contact being established between the casing and the honeycomb body via the at least one current distribution element.

[0028] The at least one current distribution element can have a height in an axial direction of the honeycomb body between 9 and 15 mm [millimeters]. The at least one current distribution element has (generally preferred) a height that substantially corresponds to the height of the honeycomb body in an axial direction.

[0029] The at least one current distribution element can have a length corresponding to a longitudinal angle of 45-180° [degrees] of a circumference of the honeycomb body. The longitudinal angle is particularly preferably between 60-120°. The longitudinal angle can be selected depending on the number and / or the distance between the ends of the tracks that extend radially from the honeycomb body. The at least one current distribution element can have a longitudinal angle such that it extends from the connection to the at least one electrode to the furthest end of the respective track of the honeycomb body to be connected.

[0030] The at least one power distribution element can be connected to two to six fastening elements. Particularly preferably, the at least one power distribution element is connected or fixedly mounted to two to four fastening elements. A higher number of fastening elements can result in better support or stiffening of the at least one power distribution element, and bending / torsion of the power distribution element can be prevented or even prevented.

[0031] The selected number of fastening elements can be arranged evenly distributed along the length of the current distribution element. However, it is also possible to provide an irregular distribution, especially if the current distribution element is not uniformly bent / curved. The at least one enclosure can be provided axially outside the gap. In other words, this means, in particular, that the enclosure is positioned axially in front of or behind the honeycomb body. The (second) end of the fastening element therefore preferably protrudes in the axial direction from the gap or beyond the honeycomb body and is enclosed there. The enclosure can be part of the casing or another (separate) part of the device (outside the honeycomb body).

[0032] In particular, at least one enclosure, which is provided axially outside the gap, can be formed on a support structure spanning the flow channel. The at least one fastening element can be held on the support structure. The support structure supports the honeycomb body with support pins distributed over the cross-section of the honeycomb body and / or along its circumferential surface. The support structure can be attached at an axial distance from the honeycomb body and supported on the inside of the casing. The support structure is arranged outside the gap, but can also cover it when viewed in the axial direction. The support structure can have an (at least partially) circumferential frame on the inside of the casing and support arms extending inward from the frame, which are supported against one another and / or against a central support hub.Preferably, the enclosures for the fastening elements are formed in the frame, and the fixing points for the support pins are formed in the support arms. The enclosure in the support structure can be designed as an approximately cylindrical receptacle that is embedded in a surface of the support structure facing the honeycomb body.

[0033] The enclosure can also be formed with the casing or on the casing outside the gap.

[0034] The flow distribution element can be mounted (indirectly) via the support element outside the gap and supported (axially) against the casing via the at least one fastening element. The design of the enclosure outside the gap is thus less spatially restricted, thus simplifying assembly. At the same time, unwanted bypass flow of exhaust gas can be significantly reduced while maintaining high stability and durability.

[0035] The at least one fastening element is preferably attached in a materially bonded manner in the frame; in particular, the at least one fastening element can be soldered or welded into the frame.

[0036] The enclosure of at least one fastening element can be provided radially outside the gap. In particular, the fastening element can extend radially outside the inside of the casing. Particularly preferably, the enclosure is then arranged on the outside of the casing. The at least one fastening element is guided through the casing via a fastening element passage. A enclosure on the outside of the casing can be designed as an annular passage.

[0037] The at least one enclosure can be provided as a (radially outward-facing) bulge in the casing. The casing can have a bulge (adjacent to the gap) at a fastener passage, in which the fastener is mounted. Such a bulge can be electrically insulated.

[0038] The at least one fastening element can thus be connected to the at least one current distribution element, protrude outward from the latter in the radial direction of the honeycomb body through the gap towards the casing, and be guided through the fastening element feedthrough into the outer enclosure. The structure of the fastening element feedthrough can be approximately the same as that of the electrode feedthrough. However, it can be provided that a (complete) cover is provided on the outside of or around the enclosure, which in particular provides moisture protection against external weather influences. A seal can be provided (on the fastening element feedthrough). The seal can seal the feedthroughs through the casing. In particular, the seal can be designed as a sleeve and / or cap.

[0039] The electrode feedthrough and the fastener feedthrough can be sealed against the surroundings of the jacket. This prevents gases contained in the jacket of the device from escaping to the environment and / or prevents gases and / or liquids contained in the environment from penetrating the jacket.

[0040] The enclosure can be electrically conductive or designed with electrical insulation. If the enclosure is arranged at a location that is electrically conductive to the surroundings of the casing, the enclosure is preferably designed with electrical insulation. Thus, electrical insulation can be provided, in particular, with an enclosure provided radially outside the gap. It is possible for electrical insulation to be provided in the enclosure on the support structure spanning the flow channel. If the fastening element already has sufficient electrical insulation, the enclosure can also be provided with an electrically conductive material, which can facilitate the production of the enclosure or the materially bonded connection of the fastening element to the enclosure.

[0041] The invention and the technical environment are explained in more detail below with reference to seven figures. The representations are schematic and not intended to illustrate proportions. The explanations given with reference to individual details of the figure are extractable and can be freely combined with facts from the above description, unless something else necessarily follows for a person skilled in the art or such a combination is explicitly excluded. It shows schematically:

[0042] Fig. 1 : a first embodiment of the device in a plan view,

[0043] Fig. 2: a detailed view of a device with current conducting element, fastening element, honeycomb body and casing, Fig. 3: a detailed view of a device with current conducting element, fastening element, enclosure, support structure and casing,

[0044] Fig. 4: a detailed view of a device with current conducting element, fastening element, enclosure, honeycomb body, support structure and casing in section,

[0045] Fig. 5: a detailed view of a device with current conducting element, fastening element, enclosure, electrical insulation, honeycomb body, support structure and casing,

[0046] Fig. 6: a detailed view of a device with current conducting element, fastening element, enclosure, electrical insulation, honeycomb body and casing in section, and

[0047] Fig. 7: an external detailed view of the device with fastener, bezel, electrical insulation and sheath.

[0048] Fig. 1 shows a device 1 in a plan view. The device 1 has a (cylindrical) casing 2, which is formed, for example, with a metal tube. The casing 2 surrounds a (main) flow channel 4 through which exhaust gases from an internal combustion engine can flow. A honeycomb body 5 is provided in the casing 2, which essentially spans the flow channel 4 and through which the exhaust gas can flow. The honeycomb body 5 shown is formed from corrugated and smooth metal foils that are joined to form packages and arranged in a meandering pattern.

[0049] Two electrodes 9 extend through the casing 2 and are each guided through the casing 2 by means of an electrode feedthrough 8. The electrodes 9 are insulated with electrical insulation 13 and each have a seal 15 on the electrode feedthrough 8. The electrodes 9 are each connected to one end of a current distribution element 7 inside the casing 2, namely adjacent to an inner side 3 of the casing 2. The current distribution elements 7 are each connected (electrically conductively) to a honeycomb body 5. In the axial direction of the honeycomb body 5 (here behind it), a support structure 12 is arranged which is connected to the casing 2 at a circumference. The support structure 12, the honeycomb body 5 and the current distribution elements 7 are arranged in a flow channel 4 which is delimited by the casing 2. The honeycomb body 5 has a circumference 14.The current distribution element 7 is arranged in a gap 6 between an inner side 3 of the casing 2 and the honeycomb body 5. The current distribution element 7 is held by several fastening elements 10, each in a frame 11. The frame 11 is arranged / formed on the support structure 12 (axially outside the gap 6).

[0050] Fig. 2 shows a detailed view of a device 1 with a current-conducting element 7, the fastening element 10, the honeycomb body 5, and the casing 2. It can be seen how the fastening elements 10 are attached laterally to the current-conducting element 7. It can also be seen that the current-conducting element 7 is arranged between the honeycomb body 5 and the inner side 3 of the casing 2.

[0051] Fig. 3 shows a detailed view of a device 1 with the current conducting element 7, the fastening element 10, the enclosure 11, the support structure 12 and the casing 2. It can be seen how the support structure 12 is attached in the flow channel 4 on the inner side 3 of the casing 2. The support structure 12 has a frame running along the casing 2, from which support arms extend inwards. In this case, enclosures for the fastening elements 10 are provided in the frame and / or the outer end section of the support arms, wherein the frame and / or support arms can be designed with (partially protruding) extension plateaus in which the enclosure is formed.

[0052] Fig. 4 shows a detailed view of a device 1 with the current-conducting element 7, the fastening element 10, the enclosure 11, the honeycomb body 5, the support structure 12 and the casing 2. An axial direction 16 and a radial direction 17 are also shown. The gap 6 is delimited in the radial direction by the inner side 3 of the casing 2 and the honeycomb body 5. In the axial direction 16, the gap 6 is delimited by the height of the honeycomb body 5. It can be seen that the enclosure 11 is arranged in the axial direction 16 outside the gap 6 in the support structure 12. In the example shown, the fastening element (top) has electrical insulation in the contact area with the current-conducting element 7, but not in the contact area towards the support element 12 (which may be made of electrically conductive material). This simplifies the joining or fitting of the fastening element 10 to the support structure 12.

[0053] Fig. 5 shows a detailed view of a device 1 with the current-conducting element 7, the fastening element 10, the enclosure 11, the electrical insulation 13, the honeycomb body 5, the support structure 12 and the casing 5. The gap 6 is delimited in the radial direction 17 by the honeycomb body 5 and the casing 2. The support structure 12 is arranged below the honeycomb body 5. It can be seen that the enclosure 11 is arranged on the casing 2 outside the gap 6 in the radial direction 17. The fastening element 10 projects from the current-conducting element 7 out of the gap 6 through the inner side 3 of the casing 2 towards the enclosure 11. In addition, the enclosure 11 is equipped with electrical insulation 13 and a seal 15.

[0054] Fig. 6 shows a detailed view of a device 1 with the current-conducting element 7, the fastening element 10, the enclosure 11, the electrical insulation 13, the honeycomb body 5, and the casing 2. It can be seen that the casing 2 forms an outward-directed bulge 18 from the gap 6, into which the fastening element 10 projects and through which it can then form the enclosure 11. In addition, the electrical insulation 13 around the fastening element 10 can be provided with / in the bulge 18 of the casing 2. A seal 15 around the fastening element 10 can be provided with or in the bulge 18 of the casing 2.

[0055] Fig. 7 shows an (external) detailed view of a device 1 with the fastening element 10, the enclosure 11, the electrical insulation 13 and the casing 2. Fig. 7 shows, like the previous Fig. 6, that the enclosure 11 is formed with an outwardly directed bulge 18 of the casing 2, the enclosure 11 being arranged radially away from the gap 6.

[0056] Reference symbol

[0057] 1 device

[0058] 2 coats

[0059] 3 Inside

[0060] 4 flow channel

[0061] 5 honeycomb bodies

[0062] 6 gap

[0063] 7 Power distribution element

[0064] 8 Electrode feedthrough

[0065] 9 Electrode

[0066] 10 Fastening element

[0067] 11 Frame

[0068] 12 Support structure

[0069] 13 electrical insulation

[0070] 14 Scope

[0071] 15 Seal

[0072] 16 axial direction

[0073] 17 radial direction

[0074] 18 bulge

Claims

Claims 1. Device (1), at least comprising a casing (2) with an inner side (3) surrounding a flow channel (4), further comprising a honeycomb body (5) positioned in the flow channel (4) and at a distance from the inner side (3), such that a gap (6) is formed between the inner side (3) and the honeycomb body (5), wherein the honeycomb body (5) is electrically conductive, and at least one current distribution element (7) partially surrounds the honeycomb body (5), wherein the device (1) further comprises at least one electrode feedthrough (8) through the casing (2), wherein at least one electrode (9) extends through the electrode feedthrough (8) as far as the at least one current distribution element (7), and the at least one current distribution element (7) is mounted at a distance from the electrode feedthrough (8) by means of at least one fastening element (10) in a frame (11) positioned outside the gap (6).

2. Device according to one of the preceding claims, wherein the at least one current distribution element (7) is electrically insulated from the at least one fastening element (10).

3. Device according to one of the preceding claims, wherein the at least one current distribution element (7) has a cross-sectional area in the range of 10 mm 2 up to 80 mm 2 has.

4. Device according to one of the preceding claims, wherein the at least one current distribution element (7) has a height in an axial direction (16) of the honeycomb body (5) in the range of 9 to 15 mm.

5. Device according to one of the preceding claims, wherein the at least one current distribution element (7) has a longitudinal angle of 45° - 180° of a circumference (14) of the honeycomb body (5).

6. Device according to one of the preceding claims, wherein the at least one enclosure (11) is provided axially outside the gap (6).

7. Device according to claim 6, wherein the at least one enclosure (11) is formed on a support structure (12) spanning the flow channel (4) and the at least one fastening element (10) is held on the support structure (12).

8. Device according to one of the preceding claims, wherein the at least one fastening element (10) is soldered or welded into the at least one enclosure (11).

9. Device according to one of the preceding claims, wherein the at least one enclosure (11) is provided radially outside the gap (6) and the at least one fastening element (10) extends through the casing (2).

10. Device according to claim 9, wherein a seal (15) is provided.

11. Device according to one of the preceding claims, wherein the enclosure (11) is electrically conductive or is provided with electrical insulation (13).

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