DE102013220055A1 - Exhaust gas treatment device - Google Patents

Abstract

The invention relates to an exhaust gas treatment device (1) with an inlet pipe (2) for introducing a combustion exhaust gas, an outlet pipe for discharging the combustion exhaust gas, at least one on the one hand with the inlet pipe (2) and on the other hand with the outlet pipe fluidly connected exhaust treatment element (4, 5) for treating the combustion exhaust gas, a jacket (7, 8) enclosing the exhaust gas treatment element (4, 5) with an outer jacket (7) and an inner jacket (8) arranged in the outer jacket (7) for enveloping the exhaust gas treatment element (4, 5), at least one the sheath (7, 8) fixedly connected bottom plate (9, 10) with an outer bottom (9) and in the outer bottom (9) arranged inner bottom (10) for closing the end of the sheath (7, 8) and an extension of the inner shell (8) formed expansion gap for compensating for a longitudinal expansion of the inner shell (8) in the direction of the bottom plate (9, 10). The invention further relates to an internal combustion engine (23) with such a device (1).

Description

The invention relates to an exhaust gas treatment device according to the preamble of claim 1 and an internal combustion engine according to the preamble of claim 16.

Methods for the mechanical, catalytic or chemical cleaning of the combustion gases of combustion, waste incineration or other industrial plants, gas turbines or engines are summarized in the exhaust gas technology under the collective term exhaust aftertreatment. An exhaust aftertreatment carried out according to the prior art, optionally in combination with other measures influencing mixture formation or combustion, significantly reduces the pollutant emissions of conventional internal combustion engines.

While for motor vehicles with gasoline engines, so-called controlled 3-way catalytic converters in many countries have long been covered by the minimum equipment required by law for public road traffic, the state of the art for exhaust fumes of comparable diesel engines for many years only provided insufficient exhaust aftertreatment because the higher air-fuel ratio of this engine variant compared to gasoline engines makes special functional demands on corresponding devices. In addition, the load of the diesel engine is not adjusted as in the Otto engine by adjusting the total volume of the air-fuel mixture, but only by changing the injected amount of fuel. By limiting the fuel supply can be realized in the case of generic diesel engines so only a slight effect on the particle emission.

The strict legal limitation of such particle emissions, the prior art therefore meets with soot filters, which are referred to the composition of the particles to be filtered as the soot particle filter (RPF) or after their origin as a diesel soot particulate filter (DPF) and a reduction in the exhaust gas stream remaining concentration of these Combustion residues aim. The reduction of the pollutant emission is also a catalyst (Kat), which often corresponds to the operating principle of the so-called oxidation catalyst or selective catalytic reduction (SCR) in combination with a diesel engine. Such filters, catalysts or thermal reactors are summarized here under the term "exhaust gas treatment device".

As an essential requirement of generic exhaust treatment devices whose effectiveness is highly coupled to the achievement and compliance with specific operating or cleaning temperatures, prove the thermal load capacity and thermal insulation against this background. The invention is therefore based on the object to provide a suitable for a wide operating temperature range exhaust gas treatment device whose shell reduces the loss of heat energy to a minimum. The invention also has the task of providing a corresponding internal combustion engine.

These objects are achieved by a device having the features of claim 1 and an internal combustion engine having the features of claim 16.

The invention is therefore based on the idea to optimize the housing of an exhaust gas treatment device with regard to possible thermally induced mechanical stresses caused by the heat transported from the combustion exhaust gas during operation of an internal combustion engine. This escaping from the combustion chamber thermal energy is transferred in the context of exhaust aftertreatment from the combustion exhaust gas to the arranged in the hot exhaust stream soot filters, catalysts and downstream components.

Although the waste heat supplied in this way can be used to achieve the technically required high operating temperatures within the assembly used for exhaust gas aftertreatment and comprising the abovementioned elements. From this point of view, the invention provides for the purpose of thermal insulation before a double-walled housing, which thermally insulated the corresponding device relative to the cooler environment.

Nevertheless, the arrangement according to the invention skilfully takes into account the temporary thermal stresses caused by the resulting inhomogeneous temperature distribution within the individual housing components, which result from the specific coefficients of thermal expansion of the materials used for the housing walls. In this respect, the invention is based, in particular, on the knowledge that the inner jacket of the device in question, which has been heated directly or indirectly by combustion exhaust gas, is subject to a considerably higher heating compared to the outer jacket surrounding it. As a result, the inner shell is thus subject to a considerable thermodynamic expansion, which has a substantially proportional effect on all dimensions of the inner shell and therefore - in absolute terms - primarily on its length measure.

The compression stress in the longitudinal direction of the inner shell caused in this way leads in the case of a conventional housing in the best case only to a plastic and / or elastic deformation of the shell end face final base plate, which more or less returns to its original shape during the subsequent cooling of the device. However, if such stresses in their sum exceed the strength of the material underlying the bottom plate, its failure can jeopardize the structural integrity of the entire case.

Against this background, a device according to the invention, in order to compensate for the physical phenomenon of longitudinal expansion of the inner shell in the direction of the bottom plate, in extension of said inner shell on a desired or tolerance gap or clearance, as commonly and also as a movement joint, dilatation, expansion joint or Designated expansion joint and about in the field of building construction to avoid so-called constraints caused by stress cracks in various trades application applies. This interruption gives the shroud a movable seat, which is able to "catch" any shifts between the inner and outer sheath within systemic limits. Such a configuration does not exclude the possibility of loose contact of the inner shell with other housing parts.

According to an advantageous embodiment of the invention, mechanical stresses on the part of the housing can be further reduced by designing the inner or outer jacket in the half-shell construction, which is known for instance from the aircraft industry, and permanently connected by means of a suitable joining method. For this purpose, for example, the connection-technical form element of the so-called fold or the flanging can be used, which combines the advantages of the outlined half-shell construction with those of a high density against the post-treated by the device combustion exhaust gas.

The desired thermal insulation of the casing can be additionally improved by means of an enclosed between the inner and outer sheath insulation mat to further favor the continuous catalytic and cleaning processes within the device on. A suitable highly elastic and thermal shock resistant technical foam, for example based on the customary polyethylene (PE) or polyurethane (PU, PUR), helps such a mat to considerable compressive strength and advantageous insulating properties. In addition, such insulation mat, if it is already compressed in the context of assembly between the inner and outer shells, a not insignificant bias of the inner shell in the direction of the inner bottom of the device to effect. An otherwise in their operation to be feared caused by vibration of the upstream engine noise in the form of a temporary or continuous rattling of the mutually striking housing elements can be largely excluded in this way.

Decisive for the absence of voltage of the overall arrangement, however, proves the applied with respect to the individual housing components mechanical connection technology. In that regard, it is primarily a matter of thinking about a material connection between the outer shell and the base plate, for example by means of soldering, gluing, vulcanization, but especially welding, which ensures a lasting cohesion of these elements by means of the atomic or molecular forces of the underlying materials. In addition, a comparable joint connection between inner and outer bottom into consideration, in order to limit the propagation of structure-borne noise within the bottom plate.

A preferred embodiment avoids the formation of known from the field of building physics constructive heat or cold bridges, which could otherwise favor an undesirable escape of thermal energy from the housing interior in zones of low heat transfer resistance. In this respect, the design of any screw-in nuts or threaded bushes, which shell, bottom plate, cover or other housing components of the device may be critical. In these problem areas, a specific dimensional relationship between the toleranced bushing to these receiving bores is recommended. Moreover, according to the invention, the circumferential edge of a cover protecting the exhaust gas treatment elements can also be optimized from the point of view of thermal insulation.

Such a threaded bush can be used, for example, for screwing in a suitable urea nozzle, as used in so-called selective catalytic reduction (SCR), in particular in vehicle technology, in order to reduce the nitrogen oxide emissions of generic diesel engines. Emission reduction efficiency can thus be significantly increased compared to pure soot particle filtration or the alternative use of a nitrogen oxide storage catalyst for the same purpose, without departing from the scope of fuel efficient combustion ratios of the upstream engine.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

It show, each schematically

1 the basic structure of the exhaust gas treatment device of an internal combustion engine according to the invention in a cross-sectional view,

2 a section of the exhaust gas treatment device in the plane AA of 1 .

3 a section of the exhaust gas treatment device in the plane BB of 1 .

4 a section of the exhaust gas treatment device in the plane UU of 1 .

5 to 25 such as 34 optional embodiments of an enlarged detail 26 of the 3 .

26 to 30 optional embodiments of an enlarged detail 27 of the 4 .

31 an enlarged detail 28 of the 3 and

32 and 33 optional embodiments of an enlarged detail 29 of the 3 ,

The 1 to 4 illustrate, starting from the cross-sectional view of 1 , The basic structure of an exhaust gas treatment device according to the invention 1 as part of an internal combustion engine 23 in the design of the conventional diesel engine. To reduce its nitrogen oxide emissions, the internal combustion engine uses 23 a selective catalytic reduction and for this purpose comprises a urea nozzle 20 which is an aqueous, about DIN 70070 corresponding urea solution in atomized form in the interior of the exhaust gas treatment device 1 passing exhaust tract of the internal combustion engine 23 feeds.

This mode of action becomes clearer on the basis of the in 2 reproduced section in the plane AA of 1 , Visible is in particular the mouth of the urea nozzle 20 in a U-shaped mixing tube 19 the exhaust treatment device 1 in which the dispersion formed by combustion exhaust gas and injected urea solution forms by hydrolysis carbon dioxide (CO ₂ ) and ammonia (NH ₃ ). The combustion exhaust gas mixed with the ammonia acting as a reducing agent then passes over one within a cap 21 formed inflow funnel 22 in an SCR catalyst 6 a, which subjects it at the appropriate operating temperature of the actual redox reaction before it via an outlet pipe 3 the exhaust treatment device 1 leaves.

As essential to the invention, however, proves the structure of the exhaust treatment device 1 in the level BB the 1 , which in the following with reference to the sectional view according to 3 is explained. The fluidic starting point of this arrangement is formed by a jacket 7 . 8th in the exhaust treatment device 1 opening hollow cylindrical inlet pipe 2 , which at high temperature from the (not shown) combustion chamber of the internal combustion engine 23 in the exhaust treatment device 1 flowing combustion exhaust gas first one - perpendicular to the inlet pipe 2 and thus substantially along the sheath 7 . 8th extending - conventional oxidation catalyst 5 supplies. The with reduced hydrocarbon (C _m H _n -) and carbon monoxide content from the oxidation catalyst 5 Exiting combustion exhaust gas then enters a downstream and in extension of the oxidation catalyst 5 arranged soot particle filter 4 over, at which the soot particles entrained by the exhaust gas stream can accumulate. The combustion exhaust gas treated in this way finally flows through the in a frontal cover 14 . 15 the exhaust treatment device 1 formed deflection chamber 16 which return it to the interior of the facility in a U-shaped flow pattern 1 leads.

In this in 3 shown sectional plane BB and in the in 4 shown, to the planes AA and BB respectively orthogonal extending cutting plane UU are four details 26 . 27 . 28 . 29 graphically highlighted and are explained below in different design variants. Attention should first be paid to the optional embodiments of the detail 26 of the 3 according to the 5 to 25 directed, which the characteristic "sliding seat construction" in the edge region of the shell 7 . 8th clarify. Visible now is the between outer jacket 7 and inner jacket 8th enclosed insulation mat 13 ,

A constructive commonality of all embodiments of the 5 to 25 is in the material separation of outer and inner sheath 7 . 8th the sheath 7 . 8th to see what the danger of thermally induced mechanical stresses in the operation of the exhaust treatment device 1 significantly reduced. A fabric closure in the form of a first weld 24 is these embodiments only between outer jacket 7 and the corresponding counter surface of the sheath 7 . 8th frontal bottom plate 9 . 10 common. As a weld is in this context analogous to Standards EN 14610 such as DIN 1910-100 any elongated connection of outer sheath, made using heat or pressure, but essentially insoluble 7 and bottom plate 9 . 10 understood, which expressly does not preclude the possible use of relevant known welding consumables.

The said first weld 24 connects the outer jacket 7 Optionally with the appropriate outdoor floor 9 the bottom plate 9 . 10 - so shown in the 5 . 6 . 7 . 10 . 11 . 14 . 15 to 20 and 22 to 25 - or with its in the outside ground 9 joined interior floor 10 - so occupied by the 8th . 9 . 12 . 13 . 16 to 19 and 21 , There is also an optional second weld 25 between outside ground 9 and inner floor 10 as they are the embodiments of 5 to 18 and 21 exhibit. The abandonment of this second weld 25 from the bottom plate 9 . 10 how the approaches according to the 19 . 20 and 22 to 25 practice, thereby opening up the possibility of a continuous insulation in the transition region of sheathing 7 . 8th and bottom plate 9 . 10 which in particular the 23 . 24 and 25 illustrate. An alternative or additional weld can - for example, according to the embodiment of 24 - Also between inner jacket 8th and inner floor 10 be provided. For all variants described is that instead of the insulation mat 13 Also air, a thermally insulating noble gas such as argon (Ar) or krypton (Kr) or the sound-insulating sulfur hexafluoride (SF ₆ ) the space between the outer and inner sheath 7 . 8th like to fill.

Another modification is the construction of the bottom plate 9 . 10 according to 34 which allows the deflection chamber (located outside the imaging limits) to be allowed 16 completely isolate. One side of the inner jacket 8th is this on the inner floor 10 by means of a weld 31 Tailored and gives the edge area of the sheath 7 . 8th a only one-sided sliding seat 32 ,

Also the detail 27 of the 4 allows a variable shape, which the 26 to 30 reflect. Regardless of the possibility of an integral version of the inner shell 8th discuss these illustrations various joining techniques approaches of a suitable half shell construction, by means of which the inner shell 8th from a first half shell 11 and a second half shell 12 is formed. The half-shells 11 . 12 are in each case substantially along a circumferential line of the inner shell 8th assembled, wherein the embodiments according to the 26 . 27 and 29 again a suitable welding technique, those according to the 28 and 30 but serve two folding techniques.

In the 31 shown detail 28 of the 3 includes one in the double-walled cover 14 . 15 provided threaded bushing 17 , wherein the structural approach shown in an analogous manner for the isolation of comparable breakthroughs in sheathing 7 . 8th , Bottom plate 9 . 10 or cap 21 can be tracked. The outer cover 14 is pierced in the present example with an outer bore diameter D1 substantially circular, which is the outer diameter of the threaded bushing 17 even approximated. The underlying inner cover 15 on the other hand, on which the underside of the threaded bush 17 partially rests, has a coaxial to this outer bore inner bore of smaller diameter D2, which is a possible tolerance offset of the outer and inner cover 14 . 15 largely compensates. The inner diameter D3 of the threaded bush 17 stands in such a way behind the inner bore diameter D2 of the inner cover 15 back that in the radial direction of the bore room for an optional, in 31 not shown weld between inner cover 15 and socket 17 remains to secure the connection of both components.

Different variants again allow the design of the detail 29 of the 3 concluded in the light of the 32 and 33 discussed and the edge area of the cover 14 . 15 concerns. For the sake of uninterrupted thermal insulation, the embodiments of both figures show an end face opposite the - outside the imaging limits of 32 . 33 extending - bottom plate 9 . 10 arranged flange 18 , which of the corresponding edge on the inner cover 15 formed support surface provides a flat counter surface.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN 70070 [0029]
• Standards EN 14610 [0033]
• DIN 1910-100 [0033]

Claims (16)

Exhaust treatment device ( 1 ), characterized by - an inlet tube ( 2 ) for introducing a combustion exhaust gas, - an outlet pipe ( 3 ) for discharging the combustion exhaust gas, - at least one on the one hand with the inlet pipe ( 2 ) and on the other hand with the outlet pipe ( 3 ) fluidically connected exhaust gas treatment element ( 4 . 5 ) for treating the combustion exhaust gas, - the exhaust gas treatment element ( 4 . 5 ) surrounding sheath ( 7 . 8th ) with an outer jacket ( 7 ) and one in the outer jacket ( 7 ) arranged inner jacket ( 8th ) for encasing the exhaust gas treatment element ( 4 . 5 ), - at least one with the sheath ( 7 . 8th ) firmly connected floor plate ( 9 . 10 ) with an outer bottom ( 9 ) and one in the outer floor ( 9 ) arranged inner bottom ( 10 ) for closing the sheath ( 7 . 8th ) and - one in extension of the inner mantle ( 8th ) expansion joint ( 30 ) for compensating for a longitudinal expansion of the inner shell ( 8th ) in the direction of the bottom plate ( 9 . 10 ). Exhaust treatment device according to claim 1, characterized by - a first half-shell ( 11 ) and - a complementary to the first half-shell ( 11 ) formed second half-shell ( 12 ), the first half shell ( 11 ) and the second half-shell ( 12 ) to the inner shell ( 8th ), in particular along a circumference of the inner shell ( 8th ) are welded or folded. Exhaust gas treatment device according to claim 1 or 2, characterized by - a between the inner shell ( 8th ) and the outer jacket ( 7 ) preferably fluid-tight enclosed insulation mat ( 13 ) for thermal insulation of the exhaust gas treatment element ( 4 . 5 ). Exhaust treatment device according to claim 3, characterized in that the insulation mat ( 13 ) elastic and the sheath ( 7 . 8th ) is such that the insulation mat ( 13 ) the inner jacket ( 8th ) in the direction of the inner floor ( 10 ). Exhaust gas treatment device according to one of claims 1 to 4, characterized in that the outer jacket ( 7 ) cohesively with the bottom plate ( 9 . 10 ), in particular along a first weld ( 24 ) is welded. Exhaust treatment device according to claim 5, characterized in that further the outer bottom ( 9 ) cohesively with the inner bottom ( 10 ), in particular along a second weld ( 25 ) is welded. Exhaust treatment device according to one of claims 1 to 6, characterized by - one opposite the bottom plate ( 9 . 10 ) arranged preferably detachable cover ( 14 . 15 ) with an outer cover ( 14 ) and an outer cover ( 15 ) for covering the exhaust gas treatment element ( 4 . 5 ). Exhaust treatment device according to claim 7, characterized by - a preferably in the cover ( 14 . 15 ), on the one hand with the exhaust gas treatment element ( 4 . 5 ) and on the other hand with the outlet pipe ( 3 ) fluidly connected deflection chamber ( 16 ) for diverting the treated combustion exhaust gas. Exhaust treatment device according to claim 7 or 8, characterized by - the outer cover ( 14 ) passing through a circular outer bore with an outer bore diameter (D1), - a coaxial with the outer bore of the inner cover ( 15 ) passing through a circular inner bore with an inner bore diameter (D2), - a threaded bushing ( 17 ) having an outer diameter substantially corresponding to the outer bore diameter (D1), an inner diameter (D3) passing below the inner bore diameter (D2) and one on the inner cover (D2). 15 ) resting bottom. Exhaust gas treatment device according to one of claims 7 to 9, characterized by - the exhaust gas treatment device ( 1 ) opposite the bottom plate ( 9 . 10 ) frontal circumferential flange ( 18 ) for placing the cover ( 14 . 15 ), the inner cover ( 15 ) has a circumferential bearing surface which is shaped so that the bearing surface flat against the flange ( 18 ) is present. Exhaust treatment device according to claim 10 in conjunction with claim 9, characterized by - a with the exhaust gas treatment element ( 4 . 5 ) Fluidically connected mixing tube ( 19 ) for mixing the treated combustion exhaust gas with an ammonia-containing reducing agent based on an aqueous urea solution, - one in the mixing tube ( 19 ), preferably in the threaded bush ( 17 ) screwed urea nozzle ( 20 ) for atomizing the urea solution and - on the one hand with the mixing tube ( 19 ) and on the other hand with the outlet pipe ( 3 ) fluidically connected SCR catalyst ( 6 ) for selectively catalytic reduction of a nitrogen oxide content of the combustion exhaust gas by means of the reducing agent. Exhaust gas treatment device according to claim 11, characterized by - a detachable with the sheath ( 7 . 8th ) connected cap ( 21 ) to cover the SCR catalyst ( 6 ). Exhaust treatment device according to claim 12, characterized by - a preferably in the cap ( 21 ), on the one hand with the mixing tube ( 19 ) and on the other hand with the SCR catalyst ( 6 ) fluidly connected inflow funnel ( 22 ) for introducing the treated combustion exhaust gas mixed with the reducing agent into the SCR catalyst ( 6 ). Exhaust treatment device according to one of claims 1 to 13, characterized in that the exhaust gas treatment element ( 4 . 5 ) a particulate filter ( 4 ), an oxidation catalyst ( 5 ), a three-way catalyst, a nitrogen oxide storage catalyst, an unregulated catalyst, or a thermal reactor. Exhaust treatment device according to one of claims 1 to 14, characterized in that one side of the inner shell ( 8th ) to the inner floor ( 10 ) preferably by means of a third weld ( 31 ) is attached. Internal combustion engine ( 23 ) with - at least one combustion chamber for combusting a fuel with the emission of a combustion exhaust gas, characterized by - an exhaust gas treatment device fluidly connected to the combustion chamber ( 1 ) according to any one of claims 1 to 15 for treating the combustion exhaust gas.

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