U.S. patent application number 13/326077 was filed with the patent office on 2012-06-28 for exhaust system and heating-up method.
This patent application is currently assigned to Bosch Emission Systems GmbH & Co. KG. Invention is credited to Harald Bressler, Bjorn Damson, Andreas Fath, Dirk Heilig, Tobias Ohrnberger.
Application Number | 20120159931 13/326077 |
Document ID | / |
Family ID | 46315081 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120159931 |
Kind Code |
A1 |
Bressler; Harald ; et
al. |
June 28, 2012 |
EXHAUST SYSTEM AND HEATING-UP METHOD
Abstract
The present invention relates to an exhaust system for a
combustion engine, particularly of a vehicle, with an oxidation
catalytic converter (oxicat), with an electrically heatable
catalytic converter (E-cat) arranged upstream of the oxicat and
with a fuel injector arranged upstream of the E-cat. An
energetically favourable mode of operation is achieved when a
particle filter is arranged downstream of the oxicat, when a bypass
path bypassing the E-cat commences downstream of the fuel injector
and ends upstream of the oxicat and when the E-cat is designed for
a smaller exhaust gas flow rate than the oxicat.
Inventors: |
Bressler; Harald;
(Stuttgart, DE) ; Heilig; Dirk; (Stuttgart,
DE) ; Damson; Bjorn; (Stuttgart, DE) ; Fath;
Andreas; (Stuttgart, DE) ; Ohrnberger; Tobias;
(Stuttgart, DE) |
Assignee: |
Bosch Emission Systems GmbH &
Co. KG
Stuttgart
DE
|
Family ID: |
46315081 |
Appl. No.: |
13/326077 |
Filed: |
December 14, 2011 |
Current U.S.
Class: |
60/274 ;
60/297 |
Current CPC
Class: |
Y02A 50/20 20180101;
Y02A 50/2322 20180101; F01N 3/035 20130101; F01N 3/2013 20130101;
F01N 3/103 20130101; Y02T 10/26 20130101; F01N 13/0097 20140603;
F01N 13/009 20140601; F01N 3/0253 20130101; F01N 3/2053 20130101;
Y02T 10/12 20130101; F01N 3/2033 20130101 |
Class at
Publication: |
60/274 ;
60/297 |
International
Class: |
F01N 3/035 20060101
F01N003/035; F01N 3/18 20060101 F01N003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2010 |
DE |
102010064020.4 |
Claims
1. An exhaust system for a combustion engine, particularly of a
vehicle, comprising: an oxidation catalytic converter (oxicat);
with an electrically heatable catalytic converter (E-cat) arranged
upstream of the oxicat; a fuel injector arranged upstream of the
E-cat; a particle filter arranged upstream of the oxicat; a bypass
path bypassing the E-cat and commencing upstream of the fuel
injector and ending downstream of the oxicat; and wherein the E-cat
is configured for a smaller exhaust gas flow rate than the
oxicat.
2. The exhaust system according to claim 1, wherein the E-cat and
oxicat are arranged in one of a common exhaust pipe or common
housing in which the bypass path is also formed.
3. The exhaust system according to claim 1, including at least one
of a configuration wherein the bypass path is throttled, and a
configuration between E-cat and oxicat a flow mixing device is
arranged.
4. The exhaust system according to claim 1, wherein between the
E-cat and oxicat at least one additional oxidation catalytic
converter (additional oxicat) is arranged so that the bypass path
bypasses the E-cat and the at least one additional oxicat, and at
least one additional bypass path that bypasses the E-cat is
provided, which commences upstream of the E-cat and ends upstream
of the additional oxicat, and wherein the at least one additional
oxicat is configured for a smaller exhaust gas flow rate than the
main oxicat, and the E-cat is designed for a smaller exhaust gas
flow rate than the additional oxicat.
5. The exhaust system according to claim 4, wherein the E-cat, main
oxicat and the at least one additional oxicat are arranged in one
of a common exhaust pipe or housing in which the main bypass path
and the at least one additional bypass path are also formed.
6. The exhaust system according to claim 4, wherein at least one
separating wall is provided, which separates the main bypass path
from the at least one additional bypass path and comprising a
configuration wherein at least one of: the main bypass path is
throttled, the additional bypass path is throttled, between the
E-cat and the at least one additional oxicat a flow mixing device
is arranged, and/or between the at least one additional oxicat and
main oxicat a flow mixing device is arranged.
7. A method for heating-up a particle filter in an exhaust system
of a combustion engine, particularly of a vehicle, comprising:
injecting fuel into a flow of engine exhaust gas transported in the
exhaust system in order to form an engine exhaust gas-fuel mixture;
wherein a part flow of the engine exhaust gas-fuel mixture is
converted in an electrically heatable catalytic converter (E-cat)
in order to form a catalytic converter waste gas; wherein the
catalytic converter waste gas is admixed to a residual flow of the
engine exhaust gas-fuel mixture in order to form a catalytic
converter waste gas-engine exhaust gas-fuel mixture; and wherein
the catalytic converter waste gas-engine exhaust gas-fuel mixture
is converted in an oxidation catalytic converter in order to form a
catalytic converter waste gas for heating-up the particle
filter.
8. The exhaust system according to claim 7, wherein the residual
flow of the engine exhaust gas-fuel mixture is conducted past the
E-cat, and wherein the residual flow of the engine exhaust gas-fuel
mixture is conducted past the E-cat so that heat from the E-cat is
transferred to the residual flow of the engine exhaust gas-fuel
mixture.
9. A method for heating-up a particle filter in an exhaust system
of a combustion engine, particularly of a vehicle, comprising:
injecting fuel into a flow of engine exhaust gas transported in the
exhaust system in order to form an engine exhaust gas-fuel mixture;
wherein a part flow of the engine exhaust gas-fuel mixture is
converted in an electrically heatable catalytic converter (E-cat)
in order to form a catalytic converter waste gas; wherein the
catalytic converter waste gas is supplied to a further part flow of
the engine exhaust gas-fuel mixture in order to form a catalytic
converter waste gas-engine exhaust gas-fuel mixture; wherein this
catalytic converter waste gas-engine exhaust gas-fuel mixture is
converted in an additional oxidation catalytic converter in order
to form a further catalytic converter waste gas; wherein the
further catalytic converter waste gas is admixed to a residual flow
of the engine exhaust gas-fuel mixture in order to form a catalytic
converter waste gas-engine exhaust gas-fuel mixture; wherein the
catalytic converter waste gas-engine exhaust gas-fuel mixture is
converted in a main oxidation catalytic converter in order to from
a catalytic converter waste gas for heating-up the particle
filter.
10. The method according to claim 9, wherein the further part flow
of the engine exhaust gas-fuel mixture is conducted past the E-cat
so that heat from the E-cat is transferred to the further part flow
of the engine exhaust gas-fuel mixture.
11. The method according to claim 9, wherein the residual flow of
the engine exhaust gas-fuel mixture is conducted past at least one
of the E-cat and the additional oxidation catalytic converter in a
heat-transferring manner so that heat from the E-cat and/or from
the additional oxidation catalytic converter is transferred to the
residual flow of the engine exhaust gas-fuel mixture.
12. The method according to claim 9, wherein the residual flow of
the engine exhaust gas-fuel mixture flows onto a porous evaporation
wall arranged upstream of one of the oxidation catalytic converter
or of the main oxidation catalytic converter, while one of the
catalytic converter waste gas coming from the E-cat or from the
additional oxidation catalytic converter flows through the
evaporation wall.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application claims priority to German
Application No. 102010064020.4, filed Dec. 23, 2010, the entire
teachings and disclosure of which are incorporated herein by
reference thereto.
FIELD OF THE INVENTION
[0002] The present invention relates to an exhaust system for a
combustion engine, particularly of a vehicle, having the features
of the preamble of Claim 1. The invention additionally relates to a
method for the heating-up of a particle filter in an exhaust system
of a combustion engine, particularly a vehicle.
BACKGROUND OF THE INVENTION
[0003] From DE 196 26 837 A1 an exhaust system is known, which
upstream of an oxidation catalytic converter, oxicat in brief,
comprises an electrically heatable catalytic converter, so-called
E-cat, wherein in addition a fuel injector is arranged upstream of
the E-cat. With the known exhaust system, a NOX-storage catalytic
converter, NOX-storage cat in brief, is additionally arranged
between the E-cat and the oxicat. Furthermore, a bypass which
bypasses the arrangement of fuel injector, E-cat ad NOX-storage cat
and re-enters upstream of the oxicat is provided with the known
exhaust system. With deactivated bypass, the entire exhaust gas
flow flows through the E-cat and the oxicat. The E-cat can be
heated electrically to the extent that reaches its minimum
operating temperature or light-off temperature. With heated-up
E-cat, fuel can be injected into the exhaust gas flow upstream of
the E-cat with the fuel injector, which is converted in the E-cat.
The highly exothermic reaction that occurs in the process generates
hot exhaust gases, with the help of which the NOX-storage cat can
be regenerated.
[0004] From DE 196 26 836 A1 a further exhaust system of this type
is known.
[0005] From DE 10 2005 015 479 A1 an exhaust system is known, which
downstream of an oxidation catalytic converter or oxicat includes a
particle filter, wherein downstream of the particle filter an
SCR-catalytic converter is additionally arranged. Upstream of the
SCR-catalytic converter a reduction agent metering device is
arranged, with the help of which a reduction agent can be injected
into the exhaust gas flow between the particle filter and the
SCR-catalytic converter. Furthermore, a bypass for bypassing the
SCR-catalytic converter is provided.
[0006] A further exhaust system with SCR-catalytic converter and
reduction agent injection is known from DE 101 28 414 A1.
[0007] Finally, from DE 100 36 401 B4 an exhaust system is known,
wherein upstream of a particle filter a NOX-storage catalytic
converter is arranged, wherein upstream of this NOX-storage
catalytic converter an oxidation catalytic converter is
arranged.
[0008] In particular with diesel engines, particle filters are used
in order to filter particles such as for example soot out of the
exhaust flow of the diesel engine. Such particle filters have to be
regenerated from time to time, which is regularly performed in that
the particle charge is burnt off. To this end, the particle filter
has to be heated until its particle charge self-ignites, the
so-called light-off. In the case of modern combustion engines which
operate with a comparatively high efficiency it can be that the
exhaust temperature in many operating states of the combustion
engine remains below the required light-off temperature, so that it
is not easily possible to regenerate the particle filter at the
desired point of time.
[0009] In principle it is possible, upstream of the particle
filter, to arrange an oxidation catalytic converter in the exhaust
line and introduce fuel into the exhaust gas upstream of the
oxidation catalytic converter. Insofar as the oxidation catalytic
converter has its minimum operating temperature, it can convert the
fuel carried along in the exhaust gas, which leads to a highly
exothermic reaction that generates hot exhaust gas, with the help
of which the particle filter can be heated up to the regeneration
temperature. However, it is such that in many operating states of
the combustion engine the exhaust temperature is not adequate to
heat the oxidation catalytic converter up to its minimum operating
temperature. In principle it is now conceivable to use an
electrically heatable catalytic converter instead of a conventional
oxidation catalytic converter which can be electrically heated up
to its minimum operating temperature. The energy expenditure
required for this purpose however is extremely high, which greatly
impairs the ecological balance of the combustion engine.
SUMMARY OF THE INVENTION
[0010] The present invention now deals with the problem of stating
an improved embodiment for a method for the heating-up of a
particle filter for an exhaust system of the type mentioned at the
outset, which is more preferably characterized in that a reliable
heating-up of the particle filter can be realised with
comparatively low energy requirement.
[0011] According to the invention, this problem is solved through
the subjects of the independent claims. Advantageous embodiments
are the subject of the dependent claims.
[0012] The invention is based on the general idea of arranging an
oxidation catalytic converter (oxicat) in an exhaust system having
a particle filter upstream thereof and to additionally arrange an
electrically heatable catalytic converter (E-cat) upstream of said
oxicat and additionally provide a fuel injector (HCI) upstream of
said E-cat. In addition, a bypass path bypassing the E-cat is
proposed, which commences downstream of the HCI and ends upstream
of the oxicat. It is now of particular importance that the E-cat is
designed for a smaller exhaust gas flow rate that the oxicat. The
proposed design results in that although the fuel is being fed to
the entire exhaust flow, only a part of the exhaust-fuel mixture
flows through the E-cat while the rest of this mixture flows
through the bypass, thus bypassing the E-cat. The E-cat dimensioned
for the small part-exhaust gas flow can be heated up to its minimum
operating temperature with comparatively little electric energy, so
that with comparatively little energy expenditure the fuel in the
part exhaust gas flow can be exothermically converted. The hot
exhaust gases of the E-cat which develop in the process intermix
with the remaining gas flow upstream of the oxicat and lead to a
heating-up of the oxicat. The oxicat can then exothermically
convert the fuel carried along in the remaining exhaust gas flow,
as a result of which the temperature in the exhaust gas is further
increased, which results in the desired heating-up of the following
particle filter.
[0013] The fundamental idea of the present invention thus consists
in heating up only a part flow of the exhaust gas-fuel mixture with
the help of an E-cat, so that the E-cat can be dimensioned
significantly smaller and thereby consumes significantly less
energy than an E-cat that is designed for the entire exhaust gas
flow.
[0014] For example, the E-cat is designed for an exhaust gas flow
rate that is between 30% and 70%, preferentially approximately at
50% of the exhaust gas flow rate for which the oxicat is
designed.
[0015] According to an advantageous embodiment, the E-cat and the
oxicat can be arranged in a common exhaust pipe or in a common
housing in which the bypass path is also formed. Because of this, a
compact design is achieved which additionally makes a contribution
that allows the heat to rapidly spread within the components.
[0016] According to another embodiment, the bypass path can be
throttled in order to make possible or control the flow through the
E-cat. Furthermore, a flow mixing device can be arranged between
E-cat and oxicat, which shortens the required mixing section and
thus supports the achievement of a compact design.
[0017] With an advantageous embodiment at least one additional
oxidation catalytic converter (additional oxicat) can be arranged
between E-cat and oxicat so that the bypass path bypasses the E-cat
and the at least one additional oxicat. In this case, the at least
one additional oxicat can be designed for a smaller exhaust gas
flow rate than the previously mentioned oxicat, which in the
following can also be called main oxicat. The E-cat in turn is
designed for a smaller exhaust gas flow rate than the additional
oxicat. With this design, only a very small exhaust gas flow rate
is captured with the help of the E-cat in order to convert the fuel
carried along therein. The hot exhaust gases resulting from this
are mixed with a further part exhaust gas flow which only bypasses
the E-cat via the additional bypass path in order to heat up the
additional oxicat so far as to convert therein the fuel of this
part flow. Only after the additional oxicat does the intermixing
with the remaining exhaust gas flow, which via the (main) bypass
path bypasses both the E-cat as well as the additional oxicat, take
place. The conversion of the remaining fuel then takes place in the
main oxicat in order to be subsequently able to heat up the
particle filer with the hot exhaust gas of the main oxicat.
[0018] For example, the additional oxicat can be designed for an
exhaust gas flow rate which is at approximately 30% to 70%,
preferentially at approximately 50% of the exhaust gas flow rate
for which the main oxicat is designed.
[0019] It is clear, furthermore, that more than one such additional
oxicat can also be provided in order to realise at least one
further stage with part conversion of the fuel.
[0020] According to another advantageous embodiment, E-cat, main
oxicat and the at least one additional oxicat can be arranged in a
common exhaust pipe or housing, in which the main bypass path and
the at least one additional bypass path are also formed. Here, too,
a compact design with improved heat transfer is supported.
[0021] With another embodiment, at least one separating wall can be
provided which separates the main bypass path from the at least one
additional bypass path. Additionally or alternatively, the main
bypass path can be throttled. Additionally or alternatively the
additional bypass path can be throttled. Additionally or
alternatively a flow mixing device can be arranged between E-cat
and additional oxicat. Additionally or alternatively a flow mixing
device can be arranged between additional oxicat and main
oxicat.
[0022] The method for the heating-up of the particle filter
proposed according to the invention thus works in such a manner
that initially fuel is injected into a flow of engine exhaust gas
transported in the exhaust system in order to form an engine
exhaust gas-fuel mixture in this manner. Subsequently, a part flow
of the engine exhaust gas-fuel mixture is converted in the E-cat in
order to form a catalytic converter waste gas in this manner. This
catalytic converter waste gas is then fed to the residual flow of
the engine exhaust gas-fuel mixture in order to form a catalytic
converter waste gas-engine exhaust gas-fuel mixture. This catalytic
converter waste gas-engine exhaust gas-fuel mixture can then be
converted in the oxidation catalytic converter in order to form a
catalytic converter waste gas for heating-up the particle
filter.
[0023] Practically, the residual flow of the engine exhaust
gas-fuel mixture can be conducted past the E-cat. It is
particularly practical here to conduct the residual flow of the
engine exhaust gas-fuel mixture past the E-cat in a heat
transferring manner so that the heat from the E-cat is transferred
to the residual flow of the engine exhaust gas-fuel mixture.
[0024] With an embodiment additionally comprising at least one
additional oxidation catalytic converter in addition to a main
oxidation catalytic converter a further part flow of the exhaust
gas-fuel mixture is admixed to the catalytic converter waste gas
originating from the E-cat in order to form a catalytic converter
waste gas-engine exhaust gas-fuel mixture. This catalytic converter
waste gas-engine exhaust gas-fuel mixture is then converted in the
mentioned additional oxidation catalytic converter in order to form
a further catalytic converter waste gas. This further catalytic
converter waste gas is then admixed to the residual flow of the
engine exhaust gas-fuel mixture so as to form a further catalytic
converter waste gas-engine exhaust gas-fuel mixture. Finally, this
further catalytic converter waste gas-engine exhaust gas-fuel
mixture is converted in the main oxidation catalytic converter in
order to form a catalytic converter waste gas for heating-up the
particle filter.
[0025] With this embodiment it is also conceivable to conduct the
further part flow of the engine exhaust gas-fuel mixture past the
E-cat in a heat-transferring manner, so that the heat from the
E-cat is transferred to the further part flow of the engine exhaust
gas-fuel mixture.
[0026] The residual flow of the engine exhaust gas-fuel mixture can
also be conducted past the E-cat and/or the additional oxidation
catalytic converter in a heat-transferring manner so that the heat
from the E-cat and/or from the additional oxidation catalytic
converter is transferred to the residual flow of the engine exhaust
gas-fuel mixture.
[0027] Of particular advantage is an embodiment, wherein the
residual flow of the engine exhaust gas-fuel mixture flows onto a
porous evaporation wall arranged upstream of the (only) oxidation
catalytic converter or upstream of the main oxidation catalytic
converter, while the catalytic converter waste gas-engine exhaust
gas-fuel mixture coming from the E-cat or from the additional
oxidation catalytic converter flows through the evaporation wall.
In other words, an already heated-up part flow of the exhaust gas
is used for heating the evaporation wall while another part of the
exhaust gas flow conducts the fuel to be evaporated to the
evaporation wall. The evaporated fuel is then discharged by the
exhaust gas flows intermixing on the evaporation wall.
[0028] Further important features and advantages of the invention
are obtained from the subclaims, from the drawings and from the
corresponding Figure description by means of the drawings.
[0029] It is to be understood that the features mentioned above and
still to be explained in the following cannot only be used in the
respective combination stated but also in other combinations or by
themselves without leaving the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Preferred exemplary embodiments of the invention are shown
in the drawings and are explained in more detail in the following
description, wherein same reference characters refer to same or
similar or functionally same components.
[0031] It shows, in each case schematically
[0032] FIGS. 1 to 4 in each case a highly simplified schematic
representation of an exhaust system in the form of a circuit
diagram with different embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0033] According to FIGS. 1 to 4 an exhaust system 1 comprises a
particle filter 2 and upstream thereof an oxidation catalytic
converter 3, which in the following can also be called oxicat 3 or
main oxidation catalytic converter 3 or main oxicat 3. Upstream of
the main oxicat 3 the exhaust system 1 additionally comprises an
electrically heatable catalytic converter 4, which in the following
is also called E-cat 4. In addition, the exhaust system 1 is
equipped with a fuel injector 5, which can also be called HC
injector 5 or HCI 5. With the help of the HC injector 5, fuel 6 can
be injected into the exhaust gas flow. The exhaust system 1 serves
for discharging exhaust gases of a combustion engine 7, which can
be arranged in a vehicle.
[0034] The exhaust system 1 introduced here additionally contains a
bypass path 8, which bypasses the E-cat 4 and in the following can
also be called main bypass path 8. The main bypass path 8 commences
between the fuel injector 5 and the E-cat 4 and ends between the
E-cat 4 and the main oxicat 3. The E-cat 4 is designed for a
smaller exhaust gas flow rate than the main oxicat 3. In operation,
the E-cat is only subjected to the throughflow of a part flow of
the engine exhaust gas generated by the combustion engine 7, while
the residual engine exhaust gas flows through the main bypass path
8 and bypasses the E-cat 4.
[0035] The embodiments shown in FIGS. 2 to 4 differ from the
embodiment shown in FIG. 1 in that additionally to the E-cat 4 and
to the main oxicat 3 an additional oxidation catalytic converter 9
is provided, which in the following can also be called additional
oxicat 9. The additional oxicat 9 in this case is fluidically
arranged between the E-cat 4 and the main oxicat 3. In addition,
the additional oxicat 9 is positioned so that the main bypass path
also bypasses the additional oxicat 9 and thus ends between the
additional oxicat 9 and the main oxicat 3. Furthermore, an
additional bypass path 10 is provided with these embodiments, which
bypasses the E-cat 4 and to this end commences upstream of the
E-cat 4 and ends between the E-cat 4 and the additional oxicat 9.
The additional oxicat 9 is designed for a smaller exhaust gas flow
rate than the main oxicat 3. In addition, the E-cat 4 with these
embodiments is designed for a smaller exhaust gas flow rate than
the additional oxicat 9. The additional bypass path 10 with the
embodiments of FIGS. 2 to 4 is realised with the help of a
separating wall 11, which divides the main bypass path 8 so that
the additional bypass path 10 ultimately represents a branch-off of
the main bypass path 8.
[0036] To achieve a compact design, the E-cat 4 and the main oxicat
3 can also be arranged in a common exhaust pipe 12. According to
FIGS. 2 and 3, the additional oxicat 9 can also be accommodated in
this common exhaust pipe 12. Alternatively, FIG. 4 shows an
embodiment wherein the E-cat 4, additional oxicat 9 and main oxicat
3 are accommodated in a common housing 13.
[0037] According to FIG. 3, the main bypass path 8 can be
throttled. A corresponding throttling point 14 is formed in FIG. 3
by a flow baffle. The additional bypass path 10 can also be
practically throttled. A corresponding throttling point 15 is
likewise indicated by a flow baffle in FIG. 3. Between the E-cat 4
and the main oxicat 3 a flow mixing device 16 can be arranged
downstream of the end of the main bypass path 8 which in the
example of FIG. 3 is formed by a flow guiding element. In
principle, a flow mixing device 17, which is arranged downstream of
the end of the additional bypass path 10 and which is represented
in FIG. 3 by a flow guiding element, can also be arranged between
the E-cat 4 and the additional oxicat 9.
[0038] The throttling points 14, 15 and/or the flow mixing devices
16, 17 are only shown exemplarily in FIG. 3. It is clear that such
throttling points and/or flow mixing devices can also be realised
in corresponding manner with the other embodiments shown in FIGS.
1, 2 and 4.
[0039] The exhaust systems 1 introduced here operate as
follows:
[0040] In order to be able to regenerate the particle filter 2 it
has to be heated to a regeneration temperature or to its light-off
temperature. With the embodiment shown in FIG. 1, this can be
realised in that with the help of the fuel injector 5 fuel 6 is
injected into a flow of engine exhaust gas 18 which is discharged
in the exhaust system 1 by the combustion engine 7. Through the
injection of the fuel 6 an engine exhaust gas-fuel mixture 19 is
formed. A part flow 20 of this engine exhaust gas-fuel mixture 19
is converted in the E-cat 4 in order to from a catalytic converter
waste gas 21. A residual flow 22 of the engine exhaust gas-fuel
mixture 19 bypasses the E-cat 4 in the bypass path 8. The mentioned
catalytic converter waste gas 21 is admixed to the residual flow 22
of the engine exhaust gas-fuel mixture 19 so as to form a catalytic
converter waste gas-engine exhaust gas-fuel mixture 23. This
catalytic converter waste gas-engine exhaust gas-fuel mixture 23 is
converted in the oxicat 3 in order to form a catalytic converter
waste gas 24 with which the particle filter 2 can be heated up.
[0041] The bypass path 8 is practically coupled in a heat
transferring manner to the E-cat so that the residual flow 22 of
the engine exhaust gas-fuel mixture 19 is preheated while flowing
through the bypass path 8.
[0042] The embodiment shown in FIGS. 2 to 4 operates as follows for
heating-up the particle filter 2.
[0043] Initially, fuel 6 is again injected into the engine exhaust
gas 18 in order to obtain the engine exhaust gas-fuel mixture 19.
Then, a part flow 20 of the engine exhaust gas-fuel mixture 19 is
again conducted through the E-cat 4 and converted therein in order
to form the catalytic converter waste gas 21. A further part flow
25 of the engine exhaust gas-fuel mixture 19 in the process
bypasses only the E-cat 4 in the additional bypass path 10 while
the residual flow 22 of the engine exhaust gas-fuel mixture 19
bypasses the E-cat 4 and the additional oxicat 9. The catalytic
converter waste gas 21 formed in the E-cat 4 is supplied with the
further part flow 25 of the engine exhaust gas-fuel mixture 19 in
order to form a catalytic converter waste gas-engine exhaust
gas-fuel mixture 26, which is subsequently converted in the
additional oxicat 9. Here, a further catalytic converter waste gas
27 is formed, which is mixed with the residual flow 22 of the
engine exhaust gas-fuel mixture 19 so as to form a further
catalytic converter waste gas-engine exhaust gas-fuel mixture 28.
This further catalytic converter waste gas-engine exhaust gas-fuel
mixture 28 is converted in the main oxicat 3 in order to form the
hot catalytic converter waste gas 24, with the help of which the
particle filter 2 can be heated up.
[0044] Practically, the arrangement of E-cat 4 and additional
oxicat 9 as well as of the bypass paths 8, 10 is made within the
exhaust pipe 2 or within the housing 13 so that on the one hand the
additional bypass path 10 is coupled to the E-cat 4 in a heat
transferring manner so that the further part flow 25 of the engine
exhaust gas-fuel mixture 19 can be preheated. On the other hand,
the main bypass path 8 can also be coupled to the E-cat 4 and to
the additional oxicat 9 in a heat-transferring manner so that the
residual flow 22 of the engine exhaust gas-fuel mixture 19 can
likewise be preheated.
[0045] With the embodiment shown in FIG. 4 a porous evaporation
wall 29 is additionally arranged in the housing 13, mainly upstream
of the main oxicat 3 and downstream of the additional oxicat 9. The
porous evaporation wall 29 on the one hand, according to FIG. 4
from the left, is subjected to an onflow by the residual flow 22 of
the engine exhaust gas-fuel mixture 19 and on the other hand,
according to FIG. 4 from the right to left, subjected to a
through-flow by catalytic converter waste gas 27 which comes from
the additional oxicat 9. On the evaporation wall 29, the fuel
carried along in the residual flow 22 of the engine exhaust
gas-fuel mixture 19 can precipitate and re-evaporate. The
evaporation heat required for this purpose then originates from the
catalytic converter waste gas 27, which flows through the
evaporation wall 29. Downstream of the evaporation wall 29 the
mixture formation additionally takes place since the catalytic
converter waste gas 27 flows through the evaporation wall 29 and
intermixes with the residual flow 22 to the catalytic converter
waste gas-engine exhaust gas-fuel mixture 28 on the outflow
side.
[0046] Insofar as such an evaporation wall 29 is to be realised
with an embodiment according to FIG. 1, the evaporation wall 29
would have to be arranged between oxicat 3 and E-cat 4. It would
then be again subjected to an onflow of residual flow 22 of the
engine exhaust gas-fuel mixture 19 on a first side and to a
through-flow of catalytic converter waste gas 21 of the E-cat 4
coming from a second side. On the first side, the catalytic
converter-engine exhaust gas-fuel mixture 23 would then form again
which flows to the oxicat 3.
* * * * *