U.S. patent application number 16/199421 was filed with the patent office on 2020-05-28 for exhaust after-treatment system having an oxidation component bypass for low temperature scr.
The applicant listed for this patent is Tenneco Automotive Operating Company Inc.. Invention is credited to Thomas M. HARRIS.
Application Number | 20200165950 16/199421 |
Document ID | / |
Family ID | 70461220 |
Filed Date | 2020-05-28 |
United States Patent
Application |
20200165950 |
Kind Code |
A1 |
HARRIS; Thomas M. |
May 28, 2020 |
EXHAUST AFTER-TREATMENT SYSTEM HAVING AN OXIDATION COMPONENT BYPASS
FOR LOW TEMPERATURE SCR
Abstract
An exhaust after-treatment system that is configured to treat an
exhaust produced by an engine, and includes a bypass passage
including an inlet for receiving an amount of the exhaust from an
exhaust passage. A first exhaust treatment component is located
within the bypass passage, and a valve is located proximate the
bypass passage that is configured to control the amount of the
exhaust that enters the inlet of the bypass passage. A second
exhaust treatment component is located in the exhaust passage
downstream from the inlet of the bypass passage, wherein an outlet
of the bypass passage communicates the exhaust treated by the first
exhaust treatment component back to the exhaust passage at a
location that is downstream from the second exhaust treatment
component such that the exhaust treated by the first exhaust
treatment component does not interact with the second exhaust
treatment component.
Inventors: |
HARRIS; Thomas M.; (Jackson,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tenneco Automotive Operating Company Inc. |
Lake Forest |
IL |
US |
|
|
Family ID: |
70461220 |
Appl. No.: |
16/199421 |
Filed: |
November 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 13/0097 20140603;
F01N 2900/1404 20130101; F01N 3/106 20130101; F01N 3/2053 20130101;
F01N 2240/36 20130101; F01N 3/035 20130101; F01N 13/0093 20140601;
F01N 3/021 20130101; F01N 3/2066 20130101; F01N 3/208 20130101;
F01N 2410/00 20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 3/035 20060101 F01N003/035; F01N 3/10 20060101
F01N003/10 |
Claims
1. An exhaust after-treatment system that is configured to treat an
exhaust produced by an engine, the system comprising: an exhaust
passage for carrying the exhaust produced by the engine; a bypass
passage including an inlet for receiving an amount of the exhaust
from the exhaust passage; a first exhaust treatment component
located within the bypass passage; a valve located proximate the
bypass passage that is configured to control the amount of the
exhaust that enters the inlet of the bypass passage; and a second
exhaust treatment component located in the exhaust passage
downstream from the inlet of the bypass passage, wherein an outlet
of the bypass passage communicates the exhaust treated by the first
exhaust treatment component back to the exhaust passage at a
location that is downstream from the second exhaust treatment
component, the exhaust treated by the first exhaust treatment
component does not interact with the second exhaust treatment
component wherein the outlet includes a length that is greater than
a length of the second exhaust treatment component, and extends
co-axially with the exhaust passage and through a center of and
outward from the second exhaust treatment component.
2. The system according to claim 1, further comprising an injector
configured to dose an exhaust treatment fluid into the exhaust
passage, the injector only being located at a single location that
is positioned upstream of the bypass passage.
3. The system according to claim 1, further comprising a third
exhaust treatment component and a fourth exhaust treatment
component in the exhaust passage and located downstream from the
second exhaust treatment component.
4. The system according to claim 1, wherein the valve is passively
controlled or actively controlled.
5. The system according to claim 4, further comprising a controller
that is configured to actively control the valve.
6-8. (canceled)
9. An exhaust after-treatment system that is configured to treat an
exhaust produced by an engine, the system comprising: an exhaust
passage for carrying the exhaust produced by the engine; a bypass
passage including an inlet for receiving an amount of the exhaust
from the exhaust passage; a first exhaust treatment component
located within the bypass passage; a valve located proximate the
bypass passage that is configured to control the amount of the
exhaust that enters the inlet of the bypass passage; and a second
exhaust treatment component located in the exhaust passage
downstream from the inlet of the bypass passage, wherein an outlet
of the bypass passage communicates the exhaust treated by the first
exhaust treatment component back to the exhaust passage at a
location that is downstream from the second exhaust treatment
component, the exhaust treated by the first exhaust treatment
component does not interact with the second exhaust treatment
component, the exhaust after-treatment system further comprising a
canister in communication with the exhaust passage, wherein the
canister houses an entirety of the bypass passage, the first
exhaust treatment component located within the bypass passage, the
valve located proximate the bypass passage, and the second exhaust
treatment component located downstream from the inlet of the bypass
passage.
10. The system according to claim 9, wherein the outlet includes a
length that is greater than a length of the second exhaust
treatment component, and extends co-axially with the exhaust
passage and through a center of and outward from the second exhaust
treatment component.
11. An exhaust after-treatment system that is configured to treat
an exhaust produced by an engine, the system comprising: an exhaust
passage for carrying the exhaust produced by the engine; a bypass
passage including an inlet for receiving an amount of the exhaust
from the exhaust passage; a first selective catalytic reduction
(SCR) component located within the bypass passage; a valve located
proximate the bypass passage that is configured to control the
amount of the exhaust that enters the inlet of the bypass passage,
and always permit an amount of the exhaust to pass through the
valve downstream from the inlet of the bypass passage; an injector
configured to dose an exhaust treatment fluid into the exhaust
passage, the injector only being located at a single location that
is positioned upstream of the bypass passage; an oxidation exhaust
treatment component located in the exhaust passage downstream from
the inlet of the bypass passage; and a second SCR component located
downstream from the oxidation exhaust treatment component, wherein
an outlet of the bypass passage communicates the exhaust treated by
the first SCR component back to the exhaust passage at a location
that is downstream from the oxidation exhaust treatment component
and upstream from the second SCR component, wherein the exhaust
treated by the first SCR component does not interact with the
oxidation exhaust treatment component, wherein the outlet includes
a length that is greater than a length of the oxidation exhaust
treatment component, and extends co-axially with the exhaust
passage and through a center of and outward from the oxidation
exhaust treatment component.
12. The system according to claim 11, further comprising a
particulate filter located downstream from the oxidation exhaust
treatment component and upstream from the second SCR component, and
a slip catalyst located downstream from the second SCR
component.
13. The system according to claim 11, further comprising a
controller that is configured to actively control the valve.
14-16. (canceled)
17. An exhaust after-treatment system that is configured to treat
an exhaust produced by an engine, the system comprising: an exhaust
passage for carrying the exhaust produced by the engine; a bypass
passage including an inlet for receiving an amount of the exhaust
from the exhaust passage; a first selective catalytic reduction
(SCR) component located within the bypass passage; a valve located
proximate the bypass passage that is configured to control the
amount of the exhaust that enters the inlet of the bypass passage,
and always permit an amount of the exhaust to pass through the
valve downstream from the inlet of the bypass passage; an injector
configured to dose an exhaust treatment fluid into the exhaust
passage, the injector only being located at a single location that
is positioned upstream of the bypass passage; an oxidation exhaust
treatment component located in the exhaust passage downstream from
the inlet of the bypass passage; and a second SCR component located
downstream from the oxidation exhaust treatment component, wherein
an outlet of the bypass passage communicates the exhaust treated by
the first SCR component back to the exhaust passage at a location
that is downstream from the oxidation exhaust treatment component
and upstream from the second SCR component, wherein the exhaust
treated by the first SCR component does not interact with the
oxidation exhaust treatment component, the exhaust after-treatment
system further comprising a canister in communication with the
exhaust passage, wherein the canister houses an entirety of the
bypass passage, the first SCR component located within the bypass
passage, the valve located proximate the bypass passage, and the
oxidation exhaust treatment component located downstream from the
inlet of the bypass passage.
18. The system according to claim 17, wherein the outlet includes a
length that is greater than a length of the oxidation exhaust
treatment component, and extends co-axially with the exhaust
passage and through a center of and outward from the oxidation
exhaust treatment component.
19. An exhaust after-treatment system that is configured to treat
an exhaust produced by an engine, the system comprising: an exhaust
passage for carrying the exhaust produced by the engine; a canister
in communication with the exhaust passage; a bypass passage
entirely provided in the canister, the bypass passage including an
inlet for receiving an amount of the exhaust that enters the
canister from the exhaust passage; a first selective catalytic
reduction (SCR) component located within the bypass passage; a
valve located in the canister proximate the bypass passage that is
configured to control the amount of the exhaust that enters the
inlet of the bypass passage, and always permit an amount of the
exhaust to pass through the valve downstream from the inlet of the
bypass passage; an injector configured to dose an exhaust treatment
fluid into the exhaust passage at a single location that is
positioned upstream of the canister; an oxidation exhaust treatment
component located in the canister downstream from the inlet of the
bypass passage; and a second SCR component located in the canister
downstream from the oxidation exhaust treatment component, wherein
an outlet of the bypass passage communicates the exhaust treated by
the first SCR component back to a location in the canister that is
downstream from the oxidation exhaust treatment component and
upstream from the second SCR component, wherein the exhaust treated
by the first SCR component does not interact with the oxidation
exhaust treatment component.
Description
FIELD
[0001] The present disclosure relates to an exhaust after-treatment
system having an oxidation component bypass for low temperature
selective catalytic reduction.
BACKGROUND
[0002] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0003] Diesel engines produce an exhaust that contains nitrogen
oxides (NOx), which is a regulated pollutant. NOx can be removed
from the exhaust using a process known as selective catalytic
reduction (SCR), which utilizes ammonia (NH.sub.3) as a chemical
reductant to react with the NOx and form nitrogen (N.sub.2) on the
surface of an SCR catalyst. The ammonia utilized in SCR is derived
from a diesel exhaust fluid (DEF), which is a mixture of urea and
water that is dosed into the engine exhaust stream. When the engine
exhaust has sufficient enthalpy (temperature and flow rate), the
water of the DEF is readily evaporated and the urea is decomposed
to ammonia as the DEF is dosed into the engine exhaust stream. If
the engine exhaust does not have sufficient enthalpy, however, the
water is not as readily evaporated and the urea does not decompose
to a sufficient extent, which can lead to the development of solid
deposits within the exhaust conduit. This typically occurs when the
ambient environment is cold, or when the engine has not been
operated for an extended period of time. In either case, the
exhaust after-treatment system has not had a sufficient amount of
time to be heated by the engine exhaust and develop the sufficient
amount of enthalpy to avoid the water not being readily evaporated
and the urea not decomposing to a sufficient extent.
[0004] One solution that has been proposed for the above-noted
problem is to modify an exhaust after-treatment system to include a
low-temperature SCR catalyst at a location upstream of a diesel
oxidation catalyst (DOC). A low-temperature SCR catalyst is able to
achieve NOx conversion to nitrogen at lower temperatures (i.e., at
cold start, or in cold weather) sooner than a SCR catalyst
component located downstream of the DOC due to the low-temperature
SCR catalyst component receiving nearly all of the exhaust enthalpy
that exits the engine. Unfortunately, there are several potential
disadvantages or trade-offs associated with the use of a
low-temperature SCR component upstream of the DOC.
[0005] Firstly, because the low-temperature SCR component must also
receive ammonia to convert the NOx to nitrogen, the after-treatment
system may require a first DEF dosing module or injector that is
specifically designated for dosing DEF for use by the
low-temperature SCR component, and a second DEF dosing module or
injector that is specifically designated for dosing DEF for use by
the primary SCR component located downstream of the DOC. The
additional dosing module or injector increases the complexity and
cost of the after-treatment system.
[0006] Secondly, an ammonia slip catalyst (ASC) must be located
between the low-temperature SCR component and the DOC to prevent or
at least substantially minimize ammonia that slips through the
low-temperature SCR component from reaching the DOC and being
oxidized to NOx or N.sub.2O.
[0007] Thirdly, in systems where the low-temperature SCR component
is designed to accept an entirety of the exhaust flow from the
engine, it is likely that the low-temperature SCR component will
need to be sized too large to be located immediately downstream
from the engine (i.e., too large to be close-coupled, or located in
the engine compartment). In contrast, such a design would require
that the low-temperature SCR component be located further
downstream from the engine and immediately upstream from the DOC.
As a result, the exhaust may lose a significant amount of enthalpy
as it travels through the lengthened section of the exhaust
passage, which may negate the benefits of the low-temperature SCR
component.
SUMMARY
[0008] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0009] According to a first aspect, the present disclosure provides
an exhaust after-treatment system that is configured to treat an
exhaust produced by an engine. The system includes an exhaust
passage for carrying the exhaust produced by the engine; a bypass
passage including an inlet for receiving an amount of the exhaust
from the exhaust passage; a first exhaust treatment component
located within the bypass passage; a valve located proximate the
bypass passage that is configured to control the amount of the
exhaust that enters the inlet of the bypass passage; and a second
exhaust treatment component located in the exhaust passage
downstream from the inlet of the bypass passage, wherein an outlet
of the bypass passage communicates the exhaust treated by the first
exhaust treatment component back to the exhaust passage at a
location that is downstream from the second exhaust treatment
component such that the exhaust treated by the first exhaust
treatment component does not interact with the second exhaust
treatment component.
[0010] The system according to the first aspect may further include
an injector configured to dose an exhaust treatment fluid into the
exhaust passage, wherein the injector is only located at a single
location that is positioned upstream of the bypass passage.
[0011] The system according to the first aspect may also further
include a third exhaust treatment component and a fourth exhaust
treatment component located downstream from the second exhaust
treatment component.
[0012] In the system according to the first aspect, the valve may
be either passively controlled or actively controlled. If the valve
is actively controlled, the system according to the first aspect
may further include a controller that is configured to actively
control the valve.
[0013] In the system according to the first aspect, the outlet of
the bypass passage may extend through the center of the second
exhaust treatment component.
[0014] Alternatively, the outlet may extend in parallel with the
exhaust passage, and include a branch that communicates the exhaust
treated by the first exhaust treatment component back to the
exhaust passage at the location that is downstream from the second
exhaust treatment component such that the exhaust treated by the
first exhaust treatment component does not interact with the second
exhaust treatment component.
[0015] The system according to the first aspect may also include a
third exhaust treatment component downstream from the second
exhaust treatment component, wherein the branch communicates the
exhaust treated by the first exhaust treatment component back to
the exhaust passage at a location that is downstream from the third
exhaust treatment component such that the exhaust treated by the
first exhaust treatment component does not interact with either the
second exhaust treatment component or the third exhaust treatment
component.
[0016] The system according to the first aspect may also include a
canister in communication with the exhaust passage, wherein the
canister houses an entirety of the bypass passage, the first
exhaust treatment component located within the bypass passage, the
valve located proximate the bypass passage, and the second exhaust
treatment component located downstream from the inlet of the bypass
passage. With such a configuration, the outlet may extend through a
center of the second exhaust treatment component.
[0017] According to a second aspect of the present disclosure,
there is provided an exhaust after-treatment system that is
configured to treat an exhaust produced by an engine that includes
an exhaust passage for carrying the exhaust produced by the engine;
a bypass passage including an inlet for receiving an amount of the
exhaust from the exhaust passage; a first selective catalytic
reduction (SCR) component located within the bypass passage; a
valve located proximate the bypass passage that is configured to
control the amount of the exhaust that enters the inlet of the
bypass passage, and always permits an amount of the exhaust to pass
through the valve downstream from the inlet of the bypass passage;
an injector configured to dose an exhaust treatment fluid into the
exhaust passage, the injector only being located at a single
location that is positioned upstream of the bypass passage; an
oxidation exhaust treatment component located in the exhaust
passage downstream from the inlet of the bypass passage; and a
second SCR component located downstream from the oxidation exhaust
treatment component, wherein an outlet of the bypass passage
communicates the exhaust treated by the first SCR component back to
the exhaust passage at a location that is downstream from the
oxidation exhaust treatment component and upstream from the second
SCR component such that the exhaust treated by the first SCR
component does not interact with the oxidation exhaust treatment
component.
[0018] The system according to the second aspect may also include a
particulate filter located downstream from the oxidation exhaust
treatment component and upstream from the second SCR component, and
a slip catalyst located downstream from the second SCR
component.
[0019] In the system according to the second aspect, there is
provided a controller that is configured to actively control the
valve.
[0020] In the system according to the second aspect, the outlet of
the bypass passage may extend through a center of the oxidation
exhaust treatment component. Alternatively, the outlet may extend
in parallel with the exhaust passage, and include a branch that
communicates the exhaust treated by the first SCR component back to
the exhaust passage at the location that is downstream from the
oxidation exhaust treatment component such that the exhaust treated
by the first SCR component does not interact with the oxidation
exhaust treatment component.
[0021] When the system according to the second aspect also includes
a particulate filter downstream from the oxidation exhaust
treatment component, the branch may communicate the exhaust treated
by the first SCR component back to the exhaust passage at a
location that is downstream from the particulate filter such that
the exhaust treated by the first SCR component does not interact
with either the oxidation exhaust treatment component or the
particulate filter.
[0022] According to the second aspect, the system may include a
canister in communication with the exhaust passage, wherein the
canister houses an entirety of the bypass passage, the first SCR
component located within the bypass passage, the valve located
proximate the bypass passage, and the oxidation exhaust treatment
component located downstream from the inlet of the bypass passage.
In this configuration, the outlet may extend through a center of
the oxidation exhaust treatment component.
[0023] According to a third aspect of the present disclosure, there
is provided an exhaust after-treatment system that is configured to
treat an exhaust produced by an engine that includes an exhaust
passage for carrying the exhaust produced by the engine; a canister
in communication with the exhaust passage; a bypass passage
entirely provided in the canister, the bypass passage including an
inlet for receiving an amount of the exhaust that enters the
canister from the exhaust passage; a first selective catalytic
reduction (SCR) component located within the bypass passage; a
valve located in the canister proximate the bypass passage that is
configured to control the amount of the exhaust that enters the
inlet of the bypass passage, and always permits an amount of the
exhaust to pass through the valve downstream from the inlet of the
bypass passage; an injector configured to dose an exhaust treatment
fluid into the exhaust passage at a single location that is
positioned upstream of the canister; an oxidation exhaust treatment
component located in the canister downstream from the inlet of the
bypass passage; and a second SCR component located in the canister
downstream from the oxidation exhaust treatment component, wherein
an outlet of the bypass passage communicates the exhaust treated by
the first SCR component back to a location in the canister that is
downstream from the oxidation exhaust treatment component and
upstream from the second SCR component such that the exhaust
treated by the first SCR component does not interact with the
oxidation exhaust treatment component.
[0024] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0025] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0026] FIG. 1 is a schematic representation of an exhaust system
according to a principle of the present disclosure;
[0027] FIG. 2 is a schematic representation of an exhaust system
according to a principle of the present disclosure; and
[0028] FIG. 3 is a schematic representation of an exhaust system
according to a principle of the present disclosure.
[0029] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0030] Example embodiments will now be described more fully with
reference to the accompanying drawings.
[0031] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
[0032] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0033] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0034] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0035] Spatially relative terms, such as "inner," "outer,"
"beneath," "below," "lower," "above," "upper," and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0036] FIG. 1 schematically illustrates an exhaust system 10
according to a first aspect of the present disclosure. Exhaust
system 10 can include at least an engine 12 in communication with a
fuel source (not shown) that, once consumed, will produce exhaust
gases that are discharged into an exhaust passage 14 having an
exhaust after-treatment system 16. Exhaust after-treatment system
16 is located downstream from engine 12, and may include a
plurality of exhaust treatment components 18, 20, 22, 24, and 26,
which can include catalyst-coated substrates or filters. In the
illustrated embodiment, component 18 may be a first or
low-temperature SCR component, component 20 may be a DOC component,
component 22 may be a diesel particulate filter (DPF) that may be
catalyst-coated, component 24 is a second SCR component, and
component 26 may be an optional second ASC component. Other known
exhaust treatment components (e.g., three-way catalysts, lean NOx
traps, etc.) may be used, without limitation. Each of exhaust
treatment components 20, 22, 24, and 26 may be enclosed in a single
housing or canister 28, if desired. Alternatively, each component
20, 22, 24, and 26 may be separately housed in a respective
canister and separated from each other by short sections of exhaust
passage 14.
[0037] In the illustrated embodiment, exhaust passage 14 includes a
bypass passage 30 that includes low-temperature SCR component 18.
Bypass passage 30 includes an inlet 32 that is branched off of
exhaust passage 14 and receives at least a portion of the engine
exhaust therein, and an outlet 34 that feeds the engine exhaust
that is treated by low-temperature SCR component 18 back to the
exhaust passage 14. To ensure that at least a portion of the engine
exhaust is forced to enter bypass passage 30 when desired, a valve
36 may be located in exhaust passage 14 immediately downstream from
inlet 32. Valve 36 may be passively controlled by, for example, a
spring (not shown) that allows valve to open when the exhaust flow
rate in exhaust passage 14 reaches a predetermined threshold, or
valve 36 may be actively controlled by an exhaust after-treatment
controller 38. Alternatively, valve 36 may be controlled by an
electronic control unit (ECU) 40 of the engine 12. When valve 36 is
actively controlled, valve 36 may be any type of electrically
controlled valve that is known to one skilled in the art.
Regardless, it should be understood that valve 36 is designed to
always allow a portion of the engine exhaust to pass through valve
36 toward exhaust treatment components 20, 22, 24, and 26. In this
manner, the amount of engine exhaust that is allowed to enter
bypass passage 30 is reduced.
[0038] More particularly, by controlling the amount of engine
exhaust that is allowed to enter bypass passage 30, a size of the
low-temperature SCR 18 can be made to be smaller (e.g., diameter
and length) in comparison to the remaining exhaust treatment
components 20, 22, 24, and 26, which allows for low-temperature
exhaust treatment component 18 to be packaged in a configuration
that runs parallel with exhaust passage 14. Moreover, the smaller
size of low-temperature SCR 18 allows for bypass passage 30 to be
closely-coupled to engine 12. In this manner, the low-temperature
SCR 18 is able to achieve SCR at lower temperatures (i.e., at cold
start, or in cold weather) sooner than the SCR catalyst component
24 located downstream due to the low-temperature SCR component 18
receiving nearly all of the exhaust enthalpy that exits the engine
12. Further, by always allowing for a portion of the engine exhaust
to pass through valve 36 toward remaining exhaust treatment
components 20, 22, 24, and 26, at least a portion of the exhaust
enthalpy is able to reach these components to assist in these
components reaching a light-off temperature in cold start and cold
weather conditions.
[0039] Although not required by the present disclosure, exhaust
after-treatment system 16 can further include components such as a
thermal enhancement device or burner (not shown) to increase a
temperature of the exhaust gases passing through exhaust passage
14. Increasing the temperature of the exhaust gas is favorable to
achieve light-off of the catalyst in the first SCR component 18 in
cold-weather conditions and upon start-up of engine 12, as well as
initiate regeneration of the DPF component 22.
[0040] To assist in reduction of the emissions produced by engine
12, exhaust after-treatment system 16 can include a dosing module
or injector 42 for periodically dosing an exhaust treatment fluid
(e.g., DEF) into the exhaust stream. As illustrated in FIG. 1,
dosing module 42 can be located upstream of low-temperature SCR
component 18 and attached to exhaust passage 14 at inlet 32 of
bypass passage 30, and is operable to inject an exhaust treatment
fluid into the exhaust stream. In this regard, dosing module 42 is
in fluid communication with a reagent tank 44 and a pump 46 by way
of inlet line 48 to dose an exhaust treatment fluid such as diesel
fuel or DEF into the exhaust passage 14 upstream of low-temperature
exhaust treatment component 18. Dosing module 42 can also be in
communication with reagent tank 44 via return line 50. Return line
50 allows for any exhaust treatment fluid not dosed into the
exhaust stream to be returned to reagent tank 44. Flow of the
exhaust treatment fluid through inlet line 48, dosing module 42,
and return line 50 also assists in cooling dosing module 42 so that
dosing module 42 does not overheat. Although not illustrated in the
drawings, dosing module 42 can be configured to include a cooling
jacket that passes a coolant around dosing module 42 to cool
it.
[0041] The amount of exhaust treatment fluid required to
effectively treat the exhaust stream may vary with load, engine
speed, exhaust gas temperature, exhaust gas flow, engine fuel
injection timing, desired NO.sub.x reduction, barometric pressure,
relative humidity, EGR rate and engine coolant temperature. A
NO.sub.x sensor or meter 52 may be positioned downstream from
exhaust treatment components 22, 24, 26, and 28. NO.sub.x sensor 52
is operable to output a signal indicative of the exhaust NO.sub.x
content to controller 38 or ECU 40. All or some of the engine
operating parameters may be supplied from engine control unit 40
via the engine/vehicle databus to controller 38. The controller 38
could also be included as part of the ECU 40. Exhaust gas
temperature, exhaust gas flow and exhaust back pressure and other
vehicle operating parameters may be measured by respective sensors,
as indicated in FIG. 1.
[0042] The amount of exhaust treatment fluid required to
effectively treat the exhaust stream can also be dependent on the
size of the engine 12. In this regard, large-scale diesel engines
used in locomotives, marine applications, and stationary
applications can have exhaust flow rates that exceed the capacity
of a single dosing module 42. Accordingly, although only a single
dosing module 42 is illustrated for dosing exhaust treatment fluid
into the exhaust passage 14, it should be understood that multiple
dosing modules 42 for reagent injection are contemplated by the
present disclosure so long as the multiple dosing modules 42 are
located upstream of low-temperature SCR component 18 at inlet 32 of
bypass passage 30. As noted above, a second injector 42 attached to
canister 28 for second SCR component 24 is not required, which
reduces system 16 complexity and cost.
[0043] In accordance with the present disclosure, the engine
exhaust that enters bypass passage 30 and is treated by
low-temperature SCR component 18 is not permitted to remix with the
engine exhaust in exhaust passage 14 downstream from valve 36 and
upstream from the DOC component 20. In contrast, outlet 34 of
bypass passage 30 enters canister 28 and includes a length 35 that
extends co-axially with exhaust passage 14 and canister 28, and
bypasses DOC component 20 by passing through a center of DOC
component 20. As illustrated, length 35 is greater than a length of
DOC component 20 such that outlet 34 extends through an entirety of
DOC component 20, and extends outward from DOC component 20.
Alternatively, although not illustrated, it should be understood
that outlet 34 may be designed to bypass each of DOC component 20
and DPF component 22 by passing through a center of each of these
components. Regardless, it should be understood that the engine
exhaust that enters bypass passage 30 and is treated by
low-temperature SCR component 18 is not permitted to remix with the
engine exhaust until it reaches a location downstream from at least
DOC component 20. Because DOC component 20 is bypassed, exhaust
after-treatment system 16 only requires injector(s) 42 at a single
location (i.e., upstream of low-temperature SCR component 18), and
does not require injectors 42 downstream from DOC component 20 and
upstream from second SCR component 24. Moreover, this configuration
does not require an ASC component to be coupled with
low-temperature SCR component 18, which enables low-temperature SCR
component 18 to be enlarged while still maintaining a package size
that is consistent with the close-coupled location of bypass
passage 30. Further, the NOx that has been treated by
low-temperature SCR component 18 to form N.sub.2 cannot be
re-oxidized by DOC component 20.
[0044] In light of the exhaust treatment fluid being dosed into the
exhaust stream at a location upstream of low-temperature SCR
component 18, a mixing device 54 may be provided in canister 28 at
location downstream of length 35 and upstream of second SCR
component 24. Mixing device 54 assists in redistributing the
ammonia before it enters and is treated by second SCR component 24.
Any mixing device 54 known to one skilled in the art may be
used.
[0045] Now referring to FIG. 2, an exhaust after-treatment system
16 according to a second aspect of the present disclosure is
illustrated. The configuration illustrated in FIG. 2 is similar to
the configuration illustrated in FIG. 1, but differs in that bypass
outlet 34 does not pass through a center of DOC component 20, but
rather runs parallel with exhaust passage 14 to a location
downstream from DOC component 20, or to a location downstream from
each of DOC component 20 and DPF component 22. In this regard,
bypass outlet 34 has a length that is selected to pass DOC
component 20 and then extend toward and into canister 28 at a
branch 34a that routes the exhaust to canister 28 at a location
downstream from DOC component 20, or extend toward and into
canister 28 at a branch 34b that routes the exhaust to canister 28
at location downstream from each of DOC component 20 and DPF
component 22. Moreover, while mixing device 54 is located between
DPF component 22 and second SCR component 24, it should be
understood that mixing device 54 may be located between DOC
component 20 and DPF component 22 without departing from the scope
of the present disclosure.
[0046] Regardless whether system 16 includes branch 34a or branch
34b, it should be understood that the engine exhaust that enters
bypass passage 30 and is treated by low-temperature SCR component
18 is not permitted to remix with the engine exhaust until it
reaches a location downstream from at least DOC component 20.
Because DOC component 20 is bypassed, exhaust after-treatment
system 16 only requires injector(s) 42 at a single location (i.e.,
upstream of low-temperature SCR component 18), and does not require
injectors 42 downstream from DOC component 20 and upstream from
second SCR component 24. Moreover, this configuration does not
require an ASC component to be coupled with low-temperature SCR
component 18, which enables low-temperature SCR component 18 to be
enlarged while still maintaining a package size that is consistent
with the close-coupled location of bypass passage 30. Further, the
NOx that has been treated by low-temperature SCR component 18 to
form N.sub.2 cannot be re-oxidized by DOC component 20. In
addition, while injector 42 is illustrated in FIG. 2 as being
attached for injection of the exhaust treatment fluid into exhaust
passage 14, it should be understood that injector(s) 42 can be
coupled to inlet 32 of bypass passage 30, if desired.
[0047] Now referring to FIG. 3, an exhaust after-treatment system
16 according to a third aspect of the present disclosure is
illustrated. Exhaust after-treatment system 16 is similar to those
illustrated in FIGS. 1 and 2, but exhaust after-treatment system 16
is entirely contained within a single canister 28. With such a
configuration, canister 28 may be closely-coupled to engine 12 so
that nearly all of the exhaust enthalpy that exits the engine 12
can be utilized to obtain conditions that can ensure that the water
of the exhaust treatment fluid can be readily evaporated and the
urea properly decomposed to a sufficient extent.
[0048] In the illustrated configuration, the engine exhaust flows
through exhaust passage 14 and enters canister 28. Upon entry into
canister 28, at least a portion of the engine exhaust can be
diverted into bypass passage 30, which is entirely located within
canister 28, by valve 36. As noted above, however, it should be
understood that at least a portion of the engine exhaust is always
permitted to pass through valve 36 toward DOC component 20, which
occurs through outlet 15. As the engine exhaust diverted by valve
36 enters inlet 32 of bypass passage 30, the engine exhaust will be
treated by low-temperature SCR component 18 and enter outlet 34 of
bypass passage 30. Outlet 34, however, does not permit the engine
exhaust treated by low-temperature SCR component 18 to remix with
the engine exhaust that has passed through valve 36 at a location
upstream of DOC component 20. In contrast, outlet 34 includes
length 35 that is designed to pass through a center of DOC
component 20 and remix with the engine exhaust at a location
downstream of DOC component 20. As illustrated, length 35 is
greater than a length of DOC component 20 such that outlet 34
extends through an entirety of DOC component 20, and extends
outward from DOC component 20. Alternatively, length 35 may be
designed to pass through a center of each of DOC component 20 and
DPF component 22.
[0049] Because DOC component 20 is bypassed, exhaust
after-treatment system 16 only requires injector(s) 42 at a single
location (i.e., upstream of low-temperature SCR component 18), and
does not require injectors 42 downstream from DOC component 20 and
upstream from second SCR component 24. Moreover, this configuration
does not require an ASC component to be coupled with
low-temperature SCR component 18, which enables low-temperature SCR
component 18 to be enlarged while still maintaining a package size
that is consistent with the close-coupled location of bypass
passage 30. Further, the NOx that has been treated by
low-temperature SCR component 18 to form N.sub.2 cannot be
re-oxidized by DOC component 20. In addition, while injector(s) 42
are illustrated in FIG. 3 as being attached to exhaust passage 14
for injection of the exhaust treatment fluid into the exhaust
stream, it should be understood that injector(s) 42 can be coupled
to an exterior of canister 28 at a location proximate bypass
passage 30.
[0050] In light of the exhaust treatment fluid being dosed into the
exhaust stream at a location upstream of low-temperature SCR
component 18, it may be desirable to provide a mixing device 54 in
canister 28 at location downstream of outlet 34 and upstream of
second SCR component 24. Mixing device 54 assists in redistributing
the ammonia before it enters and is treated by SCR component 24.
Any mixing device 54 known to one skilled in the art may be
used.
[0051] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *