U.S. patent application number 15/968195 was filed with the patent office on 2018-08-30 for mixer assembly for mixing an additive with an exhaust gas flow.
This patent application is currently assigned to Continental Automotive GmbH. The applicant listed for this patent is Continental Automotive GmbH. Invention is credited to Klaus MUELLER-HAAS.
Application Number | 20180245495 15/968195 |
Document ID | / |
Family ID | 58546256 |
Filed Date | 2018-08-30 |
United States Patent
Application |
20180245495 |
Kind Code |
A1 |
MUELLER-HAAS; Klaus |
August 30, 2018 |
MIXER ASSEMBLY FOR MIXING AN ADDITIVE WITH AN EXHAUST GAS FLOW
Abstract
A mixer arrangement for mixing an additive with an exhaust-gas
flow, having an exhaust-gas line, an exhaust gas flowing through
the exhaust-gas line in a main flow direction, and having at least
one exhaust-gas purification element which is arranged in the
exhaust-gas line and which has a casing and, arranged within the
casing, a flow-over surface for the exhaust gas. Here, the casing
of the at least one exhaust-gas purification element has a guide
structure.
Inventors: |
MUELLER-HAAS; Klaus; (Koeln,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Continental Automotive GmbH |
Hannover |
|
DE |
|
|
Assignee: |
Continental Automotive GmbH
Hannover
DE
|
Family ID: |
58546256 |
Appl. No.: |
15/968195 |
Filed: |
May 1, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2016/076308 |
Nov 1, 2016 |
|
|
|
15968195 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 3/2066 20130101;
F01N 3/206 20130101; F01N 2330/38 20130101; F01N 2610/02 20130101;
F01N 3/2892 20130101; F01N 2330/02 20130101; F01N 3/2821
20130101 |
International
Class: |
F01N 3/28 20060101
F01N003/28; F01N 3/20 20060101 F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2015 |
DE |
10 2015 221 438.9 |
Nov 1, 2016 |
DE |
10 2016 221 432.2 |
Claims
1. A mixer arrangement for mixing an additive with an exhaust-gas
flow, comprising: an exhaust-gas line; at least one exhaust-gas
purification element which is arranged in the exhaust-gas line; a
casing; a flow-over surface for the exhaust gas, the flow-over
surface arranged within the casing; a guide structure connected to
the casing of the at least one exhaust-gas purification element;
wherein an exhaust gas flows through the exhaust-gas line in a main
flow direction.
2. The mixer arrangement of claim 1, the guide structure further
comprising multiple guide elements.
3. The mixer apparatus of claim 2, wherein the multiple guide
elements are at least partially bent radially inward.
4. The mixer apparatus of claim 2, further comprising an unwound
casing, wherein the multiple guide elements are, in the unwound
casing, arranged at an angle with respect to the axial extent of
the casing.
5. The mixer apparatus of claim 2, wherein each of the multiple
guide elements further comprising the same shape.
6. The mixer apparatus of claim 2, wherein the multiple guide
elements are of asymmetrical design.
7. The mixer apparatus of claim 2, wherein two adjacent multiple
guide elements have different areas.
8. The mixer apparatus of claim 2, the multiple guide elements
further comprising substructures.
9. The mixer apparatus of claim 8, the substructures in the guide
elements further comprising embossments.
10. The mixer apparatus of claim 8, the substructures in the guide
elements further comprising perforations.
11. The mixer apparatus of claim 8, the substructures further
comprising incisions in the end regions of the respective guide
element.
12. The mixer apparatus of claim 11, wherein, in the case of the
incisions in the end regions, the individual regions may be
additionally bent.
13. The mixer arrangement of claim 1, wherein the guide structure
is formed in one piece with the casing.
14. The mixer arrangement of claim 1, wherein the guide structure
is connected to the casing.
15. The mixer arrangement of claim 1, wherein the guide structure
is connected to the casing using inductive welding.
16. The mixer apparatus of claim 1, wherein the guide structure is
arranged on the downstream-facing side of the casing of the
exhaust-gas purification element.
17. The mixer apparatus of claim 1, wherein the guide structure is
arranged on the upstream-facing side of the casing of the
exhaust-gas purification element.
18. The mixer apparatus of claim 1, the at least one exhaust-gas
purification element further comprising multiple exhaust-gas
purification elements, wherein the multiple exhaust-gas
purification elements are arranged in the exhaust-gas line.
19. The mixer apparatus of claim 18, wherein the guide structure is
arranged on at least one of the multiple exhaust-gas purification
elements which is positioned upstream of another of the multiple
exhaust-gas purification elements as viewed in the flow
direction.
20. The mixer arrangement of claim 1, the honeycomb body further
comprising a hollow cylinder with a radially internally situated
cylindrical recess.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of PCT Application
PCT/EP2016/076308, filed Nov. 1, 2016, which claims priority to
German Patent Application 10 2015 221 438.9, filed Nov. 2, 2015,
and German Patent Application 10 2015 221 432.2, filed Nov. 1,
2015. The disclosures of the above applications are incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a mixer arrangement for mixing an
additive with an exhaust-gas flow, having an exhaust-gas line, an
exhaust gas flowing through the exhaust-gas line in a main flow
direction, and having at least one exhaust-gas purification element
which is arranged in the exhaust-gas line and which has a casing
and, arranged within the casing, a flow-over surface for the
exhaust gas.
BACKGROUND OF THE INVENTION
[0003] In internal combustion engines, in particular diesel engines
or lean-burn engines, undesirably high quantities of nitrogen
oxides are formed. A suitable approach for the elimination of these
is in particular the addition of the additive ammonia, whereby, in
the presence of an excess of oxygen, the nitrogen oxides can be
reduced to form nitrogen, and the hydrogen fraction of the ammonia
bonds to form water.
[0004] It is known for additive to be introduced into the
exhaust-gas line. With the exhaust-gas flow, the additive is
transported to a selective reduction catalytic converter (SCR
catalytic converter). With the injection of the additive counter to
the main flow direction of the exhaust-gas flow, it is sought to
achieve uniform mixing of the additive with the exhaust gas. From
DE 10 2011 117 139 A1, it is known to provide a depression in the
exhaust-gas line. By means of the depression, it is sought to
realize swirling of the exhaust gas in the exhaust-gas line in
order to further improve the mixing with the additive. It has
however been found that even such depressions, despite the swirling
that is generated, generate an uneven droplet load of the additive
in relation to the cross-sectional area of the exhaust-gas line. To
achieve high nitrogen oxide reduction rates, a highly uniform
concentration distribution of the additive and a uniform
temperature distribution, in particular with regard to the
relatively cold edge region, are necessary over the cross section
of the exhaust-gas line upstream of the SCR catalytic converter. A
further disadvantage consists in that such depressions are
associated with an enlargement of the cross section of the
exhaust-gas line, whereby the exhaust-gas line requires a larger
structural space.
SUMMARY OF THE INVENTION
[0005] The invention is therefore based on the object of providing
an apparatus with which high nitrogen oxide reduction rates are
achieved.
[0006] The object is achieved according to the invention in that
the casing of the at least one exhaust-gas purification element has
a guide structure.
[0007] The guide structure is in this case not a functional element
of the exhaust-gas purification element, in particular of the
flow-over surface arranged within the casing. The guide structure
is arranged as an additional functional unit on the at least one
exhaust-gas purification element. With the arrangement of the guide
structure on the casing, it is possible for influencing of the
exhaust-gas flow and thus swirling of the exhaust-gas flow to be
achieved in a particularly simple and effective manner. The
swirling is significantly conducive to achieving that the additive
supplied in droplet form to the exhaust-gas flow is distributed
more uniformly over the entire cross section of the exhaust-gas
line, and thus the exhaust-gas aftertreatment takes place in a
manner distributed more uniformly over the entire cross section.
Likewise, as a result of the mixing, the temperature in the end
region is increased, whereby a more uniform temperature
distribution is realized. Owing to the improved utilization of the
cross section, the aftertreatment rate of the exhaust gas
increases, or the length of the exhaust-gas treatment path is
shortened while achieving the same aftertreatment rate. The
arrangement on the casing furthermore has the advantage that, in
this way, an inexpensive fastening of the guide structure to an
exhaust-gas purification element is realized. An additional carrier
structure for the fastening of the guide structure is therefore not
necessary. Furthermore, by means of the design of the guide
structure, an adaptation of the swirling to the respective
exhaust-gas line is achieved.
[0008] The adaptation of the swirling of the exhaust-gas flow by
means of the design of the guide structure is achieved in a
particularly simple manner by virtue of the guide structure having
multiple guide elements.
[0009] In a further advantageous embodiment, the guide structure is
generated in a particularly simple manner by virtue of the guide
structure being formed in one piece with the casing. In particular
in the case of a casing produced from sheet metal, the guide
structure is generated by means of corresponding cutting-out of the
sheet-metal casing in the same working step. The fastening of the
guide structure to the casing is thereby eliminated.
[0010] In a further advantageous embodiment, the guide structure is
connected to the casing. This refinement has the advantage that the
handling of the casing and guide structure during the production
and assembly processes is easier. The fastening of the guide
structure to the casing may advantageously be realized by means of
welding or stapling, for example by induction welding. It is
likewise conceivable for the guide structure to be fastened to the
casing by means of rivets or screw connections. A further advantage
consists in that, by means of the solution according to the
invention, existing exhaust-gas purification elements are enhanced
to include the guide structure.
[0011] A fastening of the guide structure to the casing of the
exhaust-gas purification element without additional fastening means
is achieved if the guide structure is pressed together with the
casing. Here, the guide structure may either be pressed into the
casing or pressed onto the casing. The pressing of the guide
structure into the casing has the advantage that the guide
structure does not increase the outer diameter of the exhaust-gas
purification apparatus, such that no additional structural space is
required with regard to the outer diameter.
[0012] In a particularly simple embodiment, the guide structure is
a cylindrical component, the casing surface of which has at least
one radially inward indentation. It is preferable for 2 to 10,
particularly preferably 3 to 8, indentations to be provided. Since
the indentations are intended to generate swirling, the demands on
the dimensional accuracy of the indentations are low, whereby the
guide structure according to the invention is manufactured at
relatively low cost.
[0013] A particularly good adaptation of the swirling of the
exhaust-gas flow to the respective exhaust-gas line is achieved, in
a further advantageous embodiment, in that the guide structure has
at least two guide elements, preferably 3 to 20 guide elements, in
particular 4 to 10 guide elements.
[0014] The swirling in the exhaust-gas flow is improved if the
guide elements are at least partially bent radially inward in the
direction of the axis of symmetry of the exhaust-gas line. Here,
"at least partially bent" is to be understood to mean that the
entire guide element or only a part of the guide element is bent
inward. Here, in the context of the invention, a bend refers both
to a discontinuous profile of the guide element, such as arises in
the case of a kink, and a continuous profile of the guide element,
if the bend is described with a radius.
[0015] Improved swirling may also be achieved by virtue of the
guide element being multiply bent. Here, it is conceivable that, in
the flow direction, the guide element may be initially bent
initially inward and subsequently also bent outward again in the
direction of the wall of the exhaust-gas line.
[0016] Further setting of the swirling of the exhaust-gas flow is
easily achieved by virtue of the individual guide elements having
different sizes and/or bends. In this way, swirling patterns in the
exhaust-gas flow that repeat in relation to the circumferential
direction is minimized. These would otherwise result in swirling
being generated over a particular sector, but swirling over the
entire circumference of the exhaust-gas flow being impeded.
[0017] In order that the guide elements project as far as possible
into the exhaust-gas flow, they must have a certain length. If the
guide elements are oriented parallel to the casing axis in the case
of an unwound casing, the required length of the metal sheet for
the production thereof is defined by the axial length of the casing
and the length of the guide elements. In a further advantageous
embodiment, the length of the metal casing sheet required for
production purposes are considerably reduced if the guide elements
are oriented at an angle with respect to the casing. By means of
this orientation, the guide elements have a considerably smaller
axial extent. In this way, the production costs are reduced.
[0018] In a simple embodiment, all of the guide elements are formed
with the same shape. This has the advantage that a punching tool
for the production of the guide elements may be designed to be
inexpensive.
[0019] Improved swirling of the gas flow is achieved with
asymmetrically designed guide elements. Asymmetrical means that the
guide elements have for example an area which deviates from a
rectangular shape.
[0020] In another embodiment, it is likewise possible for in each
case two adjacent guide elements to have different areas through
variation of the respective lengths and widths.
[0021] By means of these different shapes of the guide elements, it
is sought to prevent partially identical swirling patterns from
arising, which collectively permit little swirling over the entire
cross section of the exhaust-gas flow.
[0022] In a further advantageous embodiment, to further intensify
the swirling, the guide elements have substructures. Such
substructures may be embossments, perforations or incisions in the
end regions, wherein, in the case of the incisions in the end
regions, the individual regions may be additionally bent.
[0023] Different arrangements of the guide structure may be
advantageous depending on the field of use, that is to say
specifically the geometrical form of the exhaust-gas line, the
exhaust-gas flow with regard to throughflow rate and temperature,
the exhaust-gas purification elements used and the arrangement
thereof.
[0024] The flow-over surfaces used in exhaust-gas purification
elements generally give rise to a certain laminarization of the
exhaust-gas flow within the exhaust-gas purification element and
when the exhaust gas exits the exhaust-gas purification element.
The laminar flows not only have the disadvantage that they give
rise to and maintain non-uniformities that arise during the
injection of the additive. They also have the effect that they
maintain the temperature gradients that arise in the exhaust-gas
flow. Such temperature gradients arise as a result of exhaust-gas
purification elements having a relatively low temperature radially
at the outside. The exhaust-gas aftertreatment is therefore less
intensive in the regions. In one advantageous embodiment, the
formation of such temperature gradients in the adjoining section of
the exhaust-gas line is avoided by virtue of the guide structure
according to the invention being arranged on the downstream-facing
side of the casing of the exhaust-gas purification element. The
swirling thus generated of the emerging flow counteracts the
formation of such temperature gradients in the adjoining section of
the exhaust-gas line. The exhaust gas mixes over the entire cross
section of the exhaust-gas line, and the exhaust-gas aftertreatment
is thus improved.
[0025] This embodiment is furthermore also advantageous if the
exhaust-gas aftertreatment is performed using multiple exhaust-gas
purification elements and the guide structure is arranged on at
least one of those exhaust-gas purification elements which is
positioned upstream of the final exhaust-gas purification element
as viewed in the flow direction.
[0026] In another advantageous embodiment, the guide structure is
arranged on the casing on the upstream-facing side of the
exhaust-gas purification element. This is advantageous in
particular if the exhaust-gas flow fed to the exhaust-gas
purification element is laminar and thus has temperature gradients
in relation to the cross section of the exhaust-gas line. For these
situations, the laminar flow is changed into a turbulent flow by
means of the guide structure arranged upstream. In this way, the
exhaust-gas purification element is impinged on by a flow without
temperature gradients, which results in an improved temperature
distribution in the exhaust-gas purification element and thus
improved exhaust-gas aftertreatment. This is advantageous in
particular in the case of catalytic converters in which the
temperature distribution has a particularly great influence on the
effectiveness, such as for example catalytic converters for methane
oxidation. Likewise, with the change from a laminar to a turbulent
flow, the droplet distribution of a supplied additive in relation
to the cross section is more uniform.
[0027] The arrangement according to the invention of a guide
structure is furthermore not restricted to particular structural
forms of exhaust-gas purification elements. Aside from exhaust-gas
purification elements with cylindrical honeycomb bodies, the guide
structure may also be provided in the case of so-called ring-shaped
catalytic converters. Ring-shaped catalytic converters are
exhaust-gas purification elements which have a cylindrical recess
in their center, in the manner of a hollow cylinder, and the
honeycomb body extends around the cylindrical recess. The
exhaust-gas purification element requires no additional structural
space in an axial direction if the guide structure does not extend
beyond the axial extent of the honeycomb body. Furthermore, the
guide structure with the above-described embodiments are applied to
hollow cylindrical honeycomb bodies.
[0028] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention will be discussed in more detail on the basis
of multiple exemplary embodiments. In the figures:
[0030] FIG. 1 is a schematic illustration of a mixer
arrangement;
[0031] FIG. 2-4 show further arrangements of a mixer arrangement as
per FIG. 1,
[0032] FIG. 5 shows an exhaust-gas purification element with a
flow-over surface,
[0033] FIG. 6 shows the casing of an exhaust-gas purification
element,
[0034] FIG. 7-9 show guide elements of the guide structure,
[0035] FIG. 10 shows a further embodiment of a mixer
arrangement.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0037] FIG. 1 shows a mixer arrangement having an exhaust-gas line
1 in a motor vehicle (not illustrated in any more detail). The
arrow indicates the main flow direction of the exhaust gas flowing
through the exhaust-gas line 1. By means of an injector 2 arranged
on the exhaust-gas line 1, urea solution is injected into the
exhaust-gas flow at an angle with respect to the main flow
direction, such that the jet 3 strikes an exhaust-gas purification
element 4 approximately centrally. The exhaust-gas purification
element is an SCR catalytic converter 4. The SCR catalytic
converter 4 is composed of a schematically illustrated honeycomb
body 5, which forms a flow-over surface for the exhaust gas, and a
casing 6, which fully encloses the honeycomb body 5. On the
downstream-facing side 7 of the casing 6, a guide structure 8 is
fastened to the casing 6. The construction of the guide structure 8
is described in the following figures. During the operation of the
mixer arrangement, the injected urea solution is sprayed onto the
honeycomb body 5 and is transported through the honeycomb body 5 by
the exhaust gas. Owing to the structure of the flow-over surface,
the exhaust gas and the droplets of urea solution still contained
therein emerge from the honeycomb body 5 on the side 7
substantially as a laminar flow. The guide structure 8 disrupts the
laminar flow, such that, downstream of the guide structure 8 in the
flow direction, the laminar flow is caused to swirl and thus
changes into a turbulent flow. As a result of this swirling, more
exhaust gas comes into contact with the droplets of the urea
solution, whereby the efficiency of the exhaust-gas after treatment
is increased.
[0038] The mixer arrangement in FIG. 2 is composed of the
exhaust-gas line 1 and two SCR catalytic converters 4, 4' as
exhaust-gas purification elements. Both SCR catalytic converters 4,
4' have in each case one honeycomb body 5 and one casing 6
surrounding the honeycomb body. The SCR catalytic converter 4
arranged upstream of the final SCR catalytic converter 4' as viewed
in the flow direction has a guide structure 8 on its
downstream-facing side 7. By means of the guide structure 8, the
flow emerging from the SCR catalytic converter 4 is caused to
swirl, such that a thoroughly mixed exhaust-gas flow enters the
downstream SCR catalytic converter 4'. As a result of this
swirling, hot exhaust gas from the center of the SCR catalytic
converter 4 is mixed with the less hot exhaust gas from the regions
in the vicinity of the casing 6, such that exhaust gas entering the
SCR catalytic converter 4' exhibits greater temperature homogeneity
in relation to the cross section, which increases the efficiency of
the second SCR catalytic converter 4'.
[0039] The mixer arrangement as per FIG. 3 may be regarded as a
combination of the mixing arrangements from FIGS. 1 and 2. The
guide structure 8 causes swirling of the exhaust-gas flow emerging
from the SCR catalytic converter 4, whereby the exhaust-gas flow
entering the SCR catalytic converter 4' exhibits a more uniform
distribution both with regard to the temperature distribution but
also with regard to the droplet distribution of the injected urea
solution. In particular in the case of the distribution of the urea
solution, the guide structure 8 assists the jet 3 in order to
distribute the urea solution more uniformly over the entire cross
section.
[0040] The mixer arrangement shown in FIG. 4 differs with regard to
the exhaust-gas purification element 4. The latter has a guide
structure 8 on the upstream-facing side 9 of the casing 6. Thus,
the impinging exhaust-gas flow is influenced with a swirling action
by the exhaust-gas purification element 4 to which the exhaust-gas
flow is supplied.
[0041] FIG. 5 shows a plan view of an exhaust-gas purification
element 4, in particular an SCR catalytic converter. The
exhaust-gas purification element is composed of a casing 6 in which
a honeycomb body 5 is arranged. The honeycomb body 5 is composed of
a multiplicity of interconnected foil layers, which form the
flow-over surface for the exhaust gas. The casing 6 has a greater
length than the honeycomb body 5. The guide structure 8 is fastened
to the inner side of the free casing surface by means of induction
welding. The guide structure 8 is composed of an encircling ring 10
which bears against the inner side of the casing 6. Guide elements
11 extend in an axial direction from the ring 10. The guide
elements 11 all have the same area and shape and are bent radially
inward by virtue of the guide elements 11 being kinked in
discontinuous fashion along an edge, such that they project at an
angle of between 0.degree. and 90.degree. into the exhaust-gas
flow.
[0042] In FIG. 6, the guide structure 8 with the guide elements 11
is formed in one piece with the casing 6 of the SCR catalytic
converter 4. The casing tube 6 is illustrated in unwound form. For
the production of the casing 6, the casing tube is rolled up, such
that the two outer edges 13, 14 abut against one another. The
casing 6 may subsequently be welded. Along the edges 12, the guide
elements 11 are bent at the desired angle. To intensify the mixing
and to avoid partial swirling patterns, adjacent guide elements 11
have different shapes. This is achieved through variation of the
lengths and widths of the guide elements 11 but also by means of
bends at different angles.
[0043] The following figures show different guide elements 11. The
guide element in FIG. 7 has a multiplicity of apertures 15, such
that, as a result of the passage from one side of the guide element
11 to the other side, the exhaust gas intensifies the thorough
mixing of the exhaust-gas flow. Thorough mixing is also realized
even if, in this arrangement, depressions 15 are arranged in place
of the apertures, which depressions project as protuberances on the
opposite side of the guide element 11. These substructures effect
additional swirling and thus improve the thorough mixing.
[0044] FIG. 8 shows a guide element 11 that has not yet been bent
in a side view, which guide element has incisions on the
circumference as a substructure, and individual regions 16 are bent
in the manner of tongues out of the plane of the guide element
11.
[0045] The guide element 11 in FIG. 9 has a first region 17, in
which the guide element 11 has been bent radially inward. In a
second region 18, the guide element has been bent in the opposite
direction thereto. By means of both regions 17, 18, the guide
element 11 has a twist about its longitudinal axis 19.
[0046] FIG. 10 shows a further embodiment of a mixer arrangement,
which is directed substantially to the embodiment of the honeycomb
body 5 of the exhaust-gas purification element 4. The honeycomb
body 5 is formed as a hollow cylinder with a cylindrical recess 20
situated in the center. The guide structure 8 is arranged in the
cylindrical recess 20, preferably on the wall, which delimits the
honeycomb body 5 in a radially inward direction, of the casing 6.
In the illustration shown, the guide structure 8 is arranged at the
downstream-facing end of the exhaust-gas purification element 4. It
is however also conceivable for the exemplary embodiments described
in the above figures to be applied to a honeycomb body 5 as per
FIG. 10.
[0047] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *