U.S. patent application number 13/890123 was filed with the patent office on 2014-11-13 for exhaust aftertreatment component condition estimation and regeneration.
This patent application is currently assigned to Cummins IP, Inc.. The applicant listed for this patent is CUMMINS IP, INC.. Invention is credited to Krishna Kamasamudram, Shankar Kumar.
Application Number | 20140331644 13/890123 |
Document ID | / |
Family ID | 51863795 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140331644 |
Kind Code |
A1 |
Kumar; Shankar ; et
al. |
November 13, 2014 |
EXHAUST AFTERTREATMENT COMPONENT CONDITION ESTIMATION AND
REGENERATION
Abstract
Described herein is an apparatus for an exhaust aftertreatment
system includes a first aftertreatment component poison module that
is configured to generate a first component poison regeneration
request based on an estimated accumulation of a first poison on the
first aftertreatment component. The accumulation of the first
poison on the first aftertreatment component is based on an
estimated amount of the first poison being released from the first
aftertreatment component. The apparatus also includes a second
aftertreatment component poison module that is configured to
generate a second component poison regeneration request based on an
estimated accumulation of the first poison on the second
aftertreatment component. The accumulation of the first poison on
the second aftertreatment component is based on the estimated
amount of the first poison being released from the first
aftertreatment component.
Inventors: |
Kumar; Shankar; (Columbus,
IN) ; Kamasamudram; Krishna; (Columbus, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CUMMINS IP, INC. |
Columbus |
IN |
US |
|
|
Assignee: |
Cummins IP, Inc.
Columbus
IN
|
Family ID: |
51863795 |
Appl. No.: |
13/890123 |
Filed: |
May 8, 2013 |
Current U.S.
Class: |
60/274 ;
60/297 |
Current CPC
Class: |
F01N 2570/14 20130101;
F01N 2900/1602 20130101; F01N 2900/1614 20130101; F01N 2900/1606
20130101; F01N 9/005 20130101; Y02T 10/47 20130101; F01N 9/00
20130101; F01N 2570/22 20130101; F01N 3/103 20130101; F01N 3/2066
20130101; Y02T 10/24 20130101; F01N 2570/12 20130101; F01N
2900/0601 20130101; F01N 2250/02 20130101; F01N 2900/1621 20130101;
Y02T 10/40 20130101; Y02T 10/12 20130101 |
Class at
Publication: |
60/274 ;
60/297 |
International
Class: |
F01N 3/08 20060101
F01N003/08 |
Claims
1. An apparatus for an exhaust aftertreatment system, comprising: a
first aftertreatment component poison module configured to generate
a first component poison regeneration request based on an estimated
accumulation of a first poison on the first aftertreatment
component, the accumulation of the first poison on the first
aftertreatment component being based on an estimated amount of the
first poison being released from the first aftertreatment
component; and a second aftertreatment component poison module
configured to generate a second component poison regeneration
request based on an estimated accumulation of the first poison on
the second aftertreatment component, the accumulation of the first
poison on the second aftertreatment component being based on the
estimated amount of the first poison being released from the first
aftertreatment component.
2. The apparatus of claim 1, further comprising a poison
regeneration arbitration module configured to generate a poison
regeneration command based on an arbitration of the first and
second component poison regeneration requests.
3. The apparatus of claim 2, further comprising a time-based
regeneration module configured to generate a system regeneration
request based on a passage of a preset period of time, wherein the
poison regeneration arbitration module is configured to generate
the poison regeneration command based on an arbitration of the
first component poison regeneration request, second component
poison regeneration request, and system regeneration request.
4. The apparatus of claim 1, wherein the accumulation of the first
poison on the second aftertreatment component is based on an
estimated amount of the first poison being released from the second
aftertreatment component, the apparatus further comprising a third
aftertreatment component poison module configured to generate a
third component poison regeneration request based on an estimated
accumulation of the first poison on the third aftertreatment
component, the accumulation of the first poison on the third
aftertreatment component being based on the estimated amount of the
first poison being released from the second aftertreatment
component.
5. The apparatus of claim 1, wherein: the first aftertreatment
component poison module is configured to estimate an amount of the
first poison being stored on the first aftertreatment component,
wherein the accumulation of the first poison on the first
aftertreatment component is based on a difference between the
amount of the first poison being stored on the first aftertreatment
component and the amount of the first poison being released from
the first aftertreatment component; and the second aftertreatment
component poison module is configured to estimate an amount of the
first poison being stored on the second aftertreatment component,
wherein the accumulation of the first poison on the second
aftertreatment component is based on a difference between the
amount of the first poison being stored on the second
aftertreatment component and the amount of the first poison being
released from the second aftertreatment component.
6. The apparatus of claim 5, wherein: the amount of the first
poison being stored on the first aftertreatment component is
estimated based on a temperature of the first aftertreatment
component and a mass flow rate of exhaust gas into the first
aftertreatment component; and the amount of the first poison being
stored on the second aftertreatment component is estimated based on
a temperature of the second aftertreatment component and a mass
flow rate of exhaust gas into the second aftertreatment
component.
7. The apparatus of claim 6, wherein: the amount of the first
poison being released from the first aftertreatment component is
estimated based on the temperature of the first aftertreatment
component and the amount of the first poison being stored on the
first aftertreatment component; and the amount of the first poison
being released from the second aftertreatment component is
estimated based on the temperature of the second aftertreatment
component and the amount of the first poison being stored on the
second aftertreatment component.
8. The apparatus of claim 1, wherein the first component poison
regeneration request comprises first regeneration event parameters
and the second component poison regeneration request comprises
second regeneration event parameters, wherein the first
regeneration event parameters are different than the second
regeneration event parameters.
9. The apparatus of claim 1, wherein the first poison comprises one
of sulfur, hydrocarbon, or water.
10. The apparatus of claim 1, wherein: the first aftertreatment
component comprises one of a diesel oxidation catalyst, a diesel
particulate filter, a selective catalytic reduction catalyst, or an
ammonia oxidation catalyst; and the second aftertreatment component
comprises another one of the diesel oxidation catalyst, diesel
particulate filter, selective catalytic reduction catalyst, or
ammonia oxidation catalyst.
11. The apparatus of claim 1, further comprising: a third
aftertreatment component poison module configured to generate a
third component poison regeneration request based on an estimated
accumulation of a second poison on the first aftertreatment
component, the accumulation of the second poison on the first
aftertreatment component being based on an amount of the second
poison being released from the first aftertreatment component; and
a fourth aftertreatment component poison module configured to
generate a fourth component poison regeneration request based on an
estimated accumulation of the second poison on the second
aftertreatment component, the accumulation of the second poison on
the second aftertreatment component being based on the estimated
amount of the second poison being released from the first
aftertreatment component.
12. The apparatus of claim 2, wherein the poison regeneration
arbitration module is further configured to generate the poison
regeneration command based on an arbitration of the first, second,
third, and fourth component poison regeneration requests.
13. The apparatus of claim 1, wherein: the first aftertreatment
component poison module generates the first component poison
regeneration request when the estimated accumulation of the first
poison on the first aftertreatment component meets a first poison
accumulation threshold, the first poison accumulation threshold
corresponding with a minimum allowable performance characteristic
of the first aftertreatment component; and the second
aftertreatment component poison module generates the second
component poison regeneration request when the estimated
accumulation of the first poison on the second aftertreatment
component meets a second poison accumulation threshold, the second
poison accumulation threshold corresponding with a minimum
allowable performance characteristic of the second aftertreatment
component.
14. The apparatus of claim 13, wherein the first poison
accumulation threshold is different than the second poison
accumulation threshold.
15. The apparatus of claim 13, wherein: the first aftertreatment
component comprises one of a diesel oxidation catalyst, a selective
catalytic reduction catalyst, or an ammonia oxidation catalyst, and
the minimum allowable performance characteristic of the first
aftertreatment component comprises one of a minimum allowable NO to
NO.sub.2 oxidation efficiency, a minimum allowable NOx conversion
efficiency, or a minimum allowable ammonia oxidation efficiency,
respectively; and the second aftertreatment component comprises
another one of the diesel oxidation catalyst, selective catalytic
reduction catalyst, or ammonia oxidation catalyst, and the minimum
allowable performance characteristic of the second aftertreatment
component comprises one of the minimum allowable NO to NO.sub.2
oxidation efficiency, minimum allowable NOx conversion efficiency,
or minimum allowable ammonia oxidation efficiency, respectively
16. The apparatus of claim 1, wherein the first poison comprises
hydrocarbon, and wherein at least the first aftertreatment
component poison module comprises an exothermal module configured
to monitor an exothermal condition of the first aftertreatment
component, and wherein the first aftertreatment component poison
module generates an exothermal regeneration request when the
exothermal condition meets an exothermal condition threshold.
17. An exhaust aftertreatment system in exhaust gas receiving
communication with an internal combustion engine, comprising: a
diesel oxidation catalyst (DOC); a selective catalytic reduction
(SCR) catalyst downstream of the DOC; an ammonia oxidation (AMOX)
catalyst downstream of the SCR catalyst; a DOC poison module
configured to estimate an accumulation of a first poison on the
DOC, and configured to request regeneration of the DOC when the
accumulation of the first poison on the DOC meets a first
predetermined poison accumulation threshold corresponding with a
minimum desirable NO to NO.sub.2 oxidation efficiency of the DOC;
an SCR poison module configured to estimate an accumulation of the
first poison on the SCR catalyst, and configured to request
regeneration of the SCR catalyst when the accumulation of the first
poison on the SCR catalyst meets a second predetermined poison
accumulation threshold corresponding with a minimum desirable NOx
conversion efficiency of the SCR catalyst; and an AMOX poison
module configured to estimate an accumulation of the first poison
on the AMOX catalyst, and configured to request regeneration of the
AMOX catalyst when the accumulation of the first poison on the AMOX
catalyst meets a third predetermined poison accumulation threshold
corresponding with a minimum desirable ammonia oxidation efficiency
of the AMOX catalyst.
18. The exhaust aftertreatment system of claim 17, wherein: the DOC
poison module is further configured to estimate an amount of poison
being released from the internal combustion engine and an amount of
poison being released from the DOC, the estimate of the
accumulation of the first poison on the DOC being based on the
amount of poison being released from the internal combustion
engine; the SCR poison module is further configured to estimate an
amount of poison being released from the SCR catalyst, the estimate
of the accumulation of the first poison on the SCR catalyst being
based on the amount of poison being released from the DOC; and the
estimate of the accumulation of the first poison on the AMOX
catalyst is based on the amount of poison being released from the
SCR catalyst.
19. A method for estimating conditions of and regenerating exhaust
aftertreatment system components, comprising: estimating an
accumulated quantity of a poison on a first aftertreatment
component; commanding a regeneration of the exhaust aftertreatment
system if the accumulated quantity of the poison on the first
aftertreatment component meets a first threshold associated with a
performance characteristic of the first aftertreatment component;
estimating an accumulated quantity of the poison on a second
aftertreatment component; and commanding a regeneration of the
exhaust aftertreatment system if the accumulated quantity of the
poison on the second aftertreatment component meets a second
threshold associated with a performance characteristic of the
second aftertreatment component.
20. The method of claim 19, further comprising: determining an
amount of the poison entering the first aftertreatment component,
wherein estimating the accumulated quantity of the poison on the
first aftertreatment component is based on the amount of the poison
entering the first aftertreatment component; and estimating an
amount of poison being released from the first aftertreatment
component, wherein estimating the accumulated quantity of the
poison on the second aftertreatment component is based on the
amount of poison being released from the first aftertreatment
component.
Description
FIELD
[0001] This disclosure relates generally to internal combustion
engine systems, and more particularly to estimating the
accumulation of species on components of an exhaust aftertreatment
system and regenerating the components of the exhaust
aftertreatment system to remove the accumulation of species.
BACKGROUND
[0002] Emissions regulations for internal combustion engines have
become more stringent over recent years. Environmental concerns
have motivated the implementation of stricter emission requirements
for internal combustion engines throughout much of the world.
Governmental agencies, such as the Environmental Protection Agency
(EPA) in the United States, carefully monitor the emission quality
of engines and set acceptable emission standards, to which all
engines must comply. Consequently, the use of exhaust
aftertreatment systems on engines to reduce emissions is
increasing.
[0003] Generally, emission requirements vary according to engine
type. Emission tests for compression-ignition (diesel) engines
typically monitor the release of carbon monoxide (CO), unburned
hydrocarbons (UHC), diesel particulate matter (PM) such as ash and
soot, and nitrogen oxides (NOx). Oxidation catalysts, such as
diesel oxidation catalysts (DOC) have been implemented in exhaust
gas aftertreatment systems to oxidize at least some particulate
matter in the exhaust stream, reduce unburned hydrocarbons and CO
in the exhaust to less environmentally harmful compounds, and
oxidize nitric oxide (NO) to form nitrogen dioxide (NO.sub.2),
which is used in the NOx conversion on an selective catalytic
reduction (SCR) catalyst. To remove the particulate matter, a
particulate matter (PM) filter is typically installed downstream
from the oxidation catalyst or in conjunction with the oxidation
catalyst. However, some exhaust aftertreatment systems do not have
a PM filter. With regard to reducing NOx emissions, NOx reduction
catalysts, including SCR systems, are utilized to convert NOx (NO
and NO.sub.2 in some fraction) to N.sub.2 and other compounds.
Further, some systems include an ammonia oxidation (AMOX) catalyst
downstream of the SCR catalyst to convert at least some ammonia
slipping from the SCR catalyst to N.sub.2 and other less harmful
compounds.
[0004] Exhaust aftertreatment system components can be susceptible
to the accumulation of various materials on the components. In most
cases, such material accumulations or deposits negatively affect
the operation, performance, or efficiency of the components.
Accordingly, the materials that accumulate on aftertreatment
components and negatively affect the functionality of the
components can be considered poisons. Several poisonous materials
include sulfur, unburned hydrocarbons (HC), and water. For example,
accumulations or deposits of sulfur-containing species on the DOC
tends to decrease the conversion of NO to NO.sub.2, decrease the
conversion of HC to CO.sub.2 and heat, which affects the thermal
management of an engine system, and increase the presence or
accumulation of HC in the DOC, which correspondingly decreases the
conversion of NO to NO.sub.2. Additionally, the presence of sulfur
deposits on the SCR catalyst decreases the NOx-conversion
capability of the SCR catalyst, and the presence of sulfur deposits
on the AMOX catalyst decreases the ammonia-conversion capability of
the AMOX catalyst.
[0005] The accumulation of HC species and water on the DOC, SCR
catalyst, and AMOX catalyst can cause similar negative effects on
the functionality of these components. Additionally, accumulation
of HC species on the DOC in the presence of an increase in the
temperature of the DOC may cause uncontrolled light-off events or
runaway regeneration. Such light-off events may damage the DOC and
send damaging sintered elements of the DOC into the SCR catalyst
and AMOX catalyst.
[0006] Because of the negative side-effects of sulfur, HC, and
water species accumulation on aftertreatment components,
conventional exhaust aftertreatment systems conduct a periodic
regeneration of the components to remove the accumulated species.
Most periodic regeneration events are initiated based on the
passing of a preset period of time or a predetermined amount of
fuel consumed by the engine regardless of the amount of accumulated
poisonous species on the various components of the exhaust
aftertreatment system.
SUMMARY
[0007] The subject matter of the present application has been
developed in response to the present state of the art, and in
particular, in response to the problems and needs in the art that
have not yet been fully solved by currently available exhaust
aftertreatment systems. Accordingly, the subject matter of the
present application has been developed to provide methods, systems,
and apparatus for estimating conditions of components of an exhaust
aftertreatment system, and regenerating the system based on the
estimated conditions. Generally, according to one embodiment,
disclosed herein is an improved method, system, and apparatus for
individually and separately estimating the accumulation of a
poisonous species (e.g., sulfur, HC, and/or water) on multiple
components of an exhaust aftertreatment system, and regenerating
the multiple components of the system based on an estimated species
accumulation of a single component reaching a predetermined
threshold.
[0008] According to one embodiment, an apparatus for an exhaust
aftertreatment system includes a first aftertreatment component
poison module that is configured to generate a first component
poison regeneration request based on an estimated accumulation of a
first poison on the first aftertreatment component. The
accumulation of the first poison on the first aftertreatment
component is based on an estimated amount of the first poison being
released from the first aftertreatment component. The apparatus
also includes a second aftertreatment component poison module that
is configured to generate a second component poison regeneration
request based on an estimated accumulation of the first poison on
the second aftertreatment component. The accumulation of the first
poison on the second aftertreatment component is based on the
estimated amount of the first poison being released from the first
aftertreatment component.
[0009] According to some implementations, the apparatus also
includes a poison regeneration arbitration module that is
configured to generate a poison regeneration command based on an
arbitration of the first and second component poison regeneration
requests. The apparatus can also include a time-based regeneration
module that is configured to generate a system regeneration request
based on the passage of a preset period of time. The first poison
regeneration arbitration module can be configured to generate the
poison regeneration command based on an arbitration of the first
component poison regeneration request, second component poison
regeneration request, and system regeneration request.
[0010] In some implementations of the apparatus, the accumulation
of the first poison on the second aftertreatment component is based
on an estimated amount of the first poison being released from the
second aftertreatment component. The apparatus can further include
a third aftertreatment component poison module that is configured
to generate a third component poison regeneration request based on
an estimated accumulation of the first poison on the third
aftertreatment component. The accumulation of the first poison on
the third aftertreatment component being can be based on the
estimated amount of the first poison being released from the second
aftertreatment component.
[0011] According to certain implementations of the apparatus, the
first aftertreatment component poison module is configured to
estimate an amount of the first poison being stored on the first
aftertreatment component. The accumulation of the first poison on
the first aftertreatment component can be based on a difference
between the amount of the first poison being stored on the first
aftertreatment component and the amount of the first poison being
released from the first aftertreatment component. The second
aftertreatment component poison module can be configured to
estimate an amount of the first poison being stored on the second
aftertreatment component. The accumulation of the first poison on
the second aftertreatment component can be based on a difference
between the amount of the first poison being stored on the second
aftertreatment component and the amount of the first poison being
released from the second aftertreatment component. The amount of
the first poison being stored on the first aftertreatment component
can be estimated based on a temperature of the first aftertreatment
component and a mass flow rate of exhaust gas into the first
aftertreatment component. The amount of the first poison being
stored on the second aftertreatment component can be estimated
based on a temperature of the second aftertreatment component and a
mass flow rate of exhaust gas into the second aftertreatment
component. The amount of the first poison being released from the
first aftertreatment component can be estimated based on the
temperature of the first aftertreatment component and the amount of
the first poison being stored on the first aftertreatment
component. The amount of the first poison being released from the
second aftertreatment component can be estimated based on the
temperature of the second aftertreatment component and the amount
of the first poison being stored on the second aftertreatment
component.
[0012] In some implementations of the apparatus, the first
component poison regeneration request includes first regeneration
event parameters, and the second component poison regeneration
request includes second regeneration event parameters. The first
regeneration event parameters can be different than the second
regeneration event parameters. The first poison can be one of
sulfur, hydrocarbon, or water. The first aftertreatment component
can include one of a diesel oxidation catalyst, a diesel
particulate filter, a selective catalytic reduction catalyst, or an
ammonia oxidation catalyst, and the second aftertreatment component
can include another one of the diesel oxidation catalyst, diesel
particulate filter, selective catalytic reduction catalyst, or
ammonia oxidation catalyst.
[0013] According to some implementations, the apparatus
additionally includes a third aftertreatment component poison
module that is configured to generate a third component poison
regeneration request based on an estimated accumulation of a second
poison on the first aftertreatment component. The accumulation of
the second poison on the first aftertreatment component can be
based on an amount of the second poison being released from the
first aftertreatment component. The apparatus may also include
[0014] a fourth aftertreatment component poison module that is
configured to generate a fourth component poison regeneration
request based on an estimated accumulation of the second poison on
the second aftertreatment component. The accumulation of the second
poison on the second aftertreatment component being can be based on
the estimated amount of the second poison being released from the
first aftertreatment component. The poison regeneration arbitration
module may be configured to generate the poison regeneration
command based on an arbitration of the first, second, third, and
fourth component poison regeneration requests.
[0015] In some implementations, the first aftertreatment component
poison module generates the first component poison regeneration
request when the estimated accumulation of the first poison on the
first aftertreatment component meets a first poison accumulation
threshold. The first poison accumulation threshold can correspond
with a minimum allowable performance characteristic of the first
aftertreatment component. The second aftertreatment component
poison module can generate the second component poison regeneration
request when the estimated accumulation of the first poison on the
second aftertreatment component meets a second poison accumulation
threshold. The second poison accumulation threshold can correspond
with a minimum allowable performance characteristic of the second
aftertreatment component. The first poison accumulation threshold
can be different than the second poison accumulation threshold.
According to certain implementations, the first aftertreatment
component includes one of a diesel oxidation catalyst, a selective
catalytic reduction catalyst, or an ammonia oxidation catalyst, and
the minimum allowable performance characteristic of the first
aftertreatment component includes one of a minimum allowable NO to
NO.sub.2 oxidation efficiency, a minimum allowable NOx conversion
efficiency, or a minimum allowable ammonia oxidation efficiency,
respectively. According to yet certain implementations, the second
aftertreatment component includes another one of the diesel
oxidation catalyst, selective catalytic reduction catalyst, or
ammonia oxidation catalyst, and the minimum allowable performance
characteristic of the second aftertreatment component includes one
of the minimum allowable NO to NO.sub.2 oxidation efficiency,
minimum allowable NOx conversion efficiency, or minimum allowable
ammonia oxidation efficiency, respectively.
[0016] In some implementations of the apparatus, the first poison
includes hydrocarbon. At least the first aftertreatment component
poison module can include an exothermal module configured to
monitor an exothermal condition of the first aftertreatment
component. The first aftertreatment component poison module
generates an exothermal regeneration request when the exothermal
condition meets an exothermal condition threshold.
[0017] According to another embodiment, an exhaust aftertreatment
system in exhaust gas receiving communication with an internal
combustion engine includes a DOC, an SCR catalyst downstream of the
DOC, and an AMOX catalyst downstream of the SCR catalyst. The
system also includes a DOC poison module that is configured to
estimate an accumulation of a first poison on the DOC, and
configured to request regeneration of the DOC when the accumulation
of the first poison on the DOC meets a first predetermined poison
accumulation threshold corresponding with a minimum desirable NO to
NO.sub.2 oxidation efficiency of the DOC. Additionally, the system
includes an SCR poison module that is configured to estimate an
accumulation of the first poison on the SCR catalyst, and
configured to request regeneration of the SCR catalyst when the
accumulation of the first poison on the SCR catalyst meets a second
predetermined poison accumulation threshold corresponding with a
minimum desirable NOx conversion efficiency of the SCR catalyst.
Also, the system includes an AMOX poison module that is configured
to estimate an accumulation of the first poison on the AMOX
catalyst, and configured to request regeneration of the AMOX
catalyst when the accumulation of the first poison on the AMOX
catalyst meets a third predetermined poison accumulation threshold
corresponding with a minimum desirable ammonia oxidation efficiency
of the AMOX catalyst.
[0018] In some implementations of the system, the DOC poison module
is further configured to estimate an amount of poison being
released from the internal combustion engine and an amount of
poison being released from the DOC. The estimate of the
accumulation of the first poison on the DOC can be based on the
amount of poison being released from the internal combustion
engine. The SCR poison module can be further configured to estimate
an amount of poison being released from the SCR catalyst. The
estimate of the accumulation of the first poison on the SCR
catalyst can be based on the amount of poison being released from
the DOC. The estimate of the accumulation of the first poison on
the AMOX catalyst can be based on the amount of poison being
released from the SCR catalyst.
[0019] In yet another embodiment, a method for estimating
conditions of and regenerating exhaust aftertreatment system
components include estimating an accumulated quantity of a poison
on a first aftertreatment component. The method also includes
commanding a regeneration of the exhaust aftertreatment system if
the accumulated quantity of the poison on the first aftertreatment
component meets a first threshold associated with a performance
characteristic of the first aftertreatment component. Further, the
method includes estimating an accumulated quantity of the poison on
a second aftertreatment component, and commanding a regeneration of
the exhaust aftertreatment system if the accumulated quantity of
the poison on the second aftertreatment component meets a second
threshold associated with a performance characteristic of the
second aftertreatment component.
[0020] In some implementations, the method includes determining an
amount of the poison entering the first aftertreatment component.
Estimating the accumulated quantity of the poison on the first
aftertreatment component can be based on the amount of the poison
entering the first aftertreatment component. The method may also
include estimating an amount of poison being released from the
first aftertreatment component. Estimating the accumulated quantity
of the poison on the second aftertreatment component can be based
on the amount of poison being released from the first
aftertreatment component.
[0021] In certain embodiments, the modules of the apparatus
described herein may each include at least one of logic hardware
and executable code, the executable code being stored on one or
more memory devices. The executable code may be replaced with a
computer processor and computer-readable storage medium that stores
executable code executed by the processor.
[0022] Reference throughout this specification to features,
advantages, or similar language does not imply that all of the
features and advantages that may be realized with the subject
matter of the present disclosure should be or are in any single
embodiment. Rather, language referring to the features and
advantages is understood to mean that a specific feature,
advantage, or characteristic described in connection with an
embodiment is included in at least one embodiment of the present
disclosure. Thus, discussion of the features and advantages, and
similar language, throughout this specification may, but do not
necessarily, refer to the same embodiment.
[0023] The described features, structures, advantages, and/or
characteristics of the subject matter of the present disclosure may
be combined in any suitable manner in one or more embodiments
and/or implementations. In the following description, numerous
specific details are provided to impart a thorough understanding of
embodiments of the subject matter of the present disclosure. One
skilled in the relevant art will recognize that the subject matter
of the present disclosure may be practiced without one or more of
the specific features, details, components, materials, and/or
methods of a particular embodiment or implementation. In other
instances, additional features and advantages may be recognized in
certain embodiments and/or implementations that may not be present
in all embodiments or implementations. Further, in some instances,
well-known structures, materials, or operations are not shown or
described in detail to avoid obscuring aspects of the subject
matter of the present disclosure. The features and advantages of
the subject matter of the present disclosure will become more fully
apparent from the following description and appended claims, or may
be learned by the practice of the subject matter as set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order that the advantages of the subject matter may be
more readily understood, a more particular description of the
subject matter briefly described above will be rendered by
reference to specific embodiments that are illustrated in the
appended drawings. Understanding that these drawings depict only
typical embodiments of the subject matter and are not therefore to
be considered to be limiting of its scope, the subject matter will
be described and explained with additional specificity and detail
through the use of the drawings, in which:
[0025] FIG. 1 is a schematic diagram of an engine system having an
internal combustion engine and an exhaust aftertreatment system in
accordance with one representative embodiment;
[0026] FIG. 2 is a schematic block diagram of a controller of the
engine system of FIG. 1 in accordance with one representative
embodiment;
[0027] FIG. 3 is a schematic block diagram of a sulfur oxidation
module of the controller of FIG. 2 in accordance with one
representative embodiment;
[0028] FIG. 4 is a schematic block diagram of a hydrocarbon
oxidation module of the controller of FIG. 2 in accordance with one
representative embodiment; and
[0029] FIG. 5 is a schematic flow chart diagram of a method for
diagnosing a condition of an exhaust aftertreatment component and
correspondingly regenerating the component in accordance with one
representative embodiment.
DETAILED DESCRIPTION
[0030] FIG. 1 depicts one embodiment of an engine system 10. The
main components of the engine system 10 include an internal
combustion engine 20 and an exhaust aftertreatment system 22 in
exhaust gas-receiving communication with the engine 20. The
internal combustion engine 20 can be a compression-ignited internal
combustion engine, such as a diesel-fueled engine, or a
spark-ignited internal combustion engine, such as a gasoline-fueled
engine operated lean. Although not shown, on the air intake side,
the engine system 10 can include an air inlet, inlet piping, a
turbocharger compressor, and an intake manifold. The intake
manifold includes an outlet that is operatively coupled to
compression chambers of the internal combustion engine 20 for
introducing air into the compression chambers.
[0031] Within the internal combustion engine 20, air from the
atmosphere is combined with fuel, and combusted, to power the
engine. The fuel comes from a fuel tank (not shown) through a fuel
delivery system including, in one embodiment, a fuel pump and
common rail to the fuel injectors, which inject fuel into the
combustion chambers of the engine 20. Fuel injection timing can be
controlled by the controller 100 via a fuel injector control
signal.
[0032] Combustion of the fuel and air in the compression chambers
of the engine 20 produces exhaust gas that is operatively vented to
an exhaust manifold (not shown). From the exhaust manifold, a
portion of the exhaust gas may be used to power a turbocharger
turbine. The turbocharger turbine drives the turbocharger
compressor, which may compress at least some of the air entering
the air inlet before directing it to the intake manifold and into
the compression chambers of the engine 20.
[0033] The exhaust aftertreatment system 22 includes the controller
100 (which also can form part of the overall engine system 10), an
optional diesel particular filter (DPF) 40, a diesel oxidation
catalyst (DOC) 30, a selective catalytic reduction (SCR) system 52
with an SCR catalyst 50, and an ammonia oxidation (AMOX) catalyst
60. The SCR system 52 further includes a reductant delivery system
that has a diesel exhaust fluid (DEF) source 54 that supplies DEF
to a DEF doser 56 via a DEF or reductant delivery line 58.
[0034] In an exhaust flow direction, as indicated by directional
arrow 29, exhaust gas flows from the engine 20 into inlet piping 24
of the exhaust aftertreatment system 22. From the inlet piping 24,
the exhaust gas flows into the DOC 30 and exits the DOC into a
first section of exhaust piping 28A. From the first section of
exhaust piping 28A, the exhaust gas flows into the DPF 40 if
present and exits the DPF into a second section of exhaust piping
28B. From the second section of exhaust piping 28B, the exhaust gas
flows into the SCR catalyst 50 and exits the SCR catalyst into the
third section of exhaust piping 28C. As the exhaust gas flows
through the second section of exhaust piping 28B, it is
periodically dosed with DEF by the DEF doser 56. Accordingly, the
second section of exhaust piping 28B acts as a decomposition
chamber or tube to facilitate the decomposition of the DEF to
ammonia. From the third section of exhaust piping 28C, the exhaust
gas flows into the AMOX catalyst 60 and exits the AMOX catalyst
into outlet piping 26 before the exhaust gas is expelled from the
system 22. Based on the foregoing, in the illustrated embodiment,
the DOC 30 is position upstream of the DPF 40 if present and the
SCR catalyst 50, and the SCR catalyst 50 is positioned downstream
of the DPF 40 when present and upstream of the AMOX catalyst 60.
However, in alternative embodiments, other arrangements of the
components of the exhaust aftertreatment system 22 are also
possible.
[0035] The DOC 30 can have any of various flow-through designs
known in the art. Generally, the DOC 30 is configured to oxidize at
least some particulate matter, e.g., the soluble organic fraction
of soot, in the exhaust and reduce unburned hydrocarbons and CO in
the exhaust to less environmentally harmful compounds. For example,
the DOC 30 may sufficiently reduce the hydrocarbon and CO
concentrations in the exhaust to meet the requisite emissions
standards for those components of the exhaust gas. An indirect
consequence of the oxidation capabilities of the DOC 30 is the
ability of the DOC to oxidize NO into NO.sub.2. In this manner, the
level of NO.sub.2 exiting the DOC 30 is equal to the NO.sub.2 in
the exhaust gas generated by the engine 20 plus the NO.sub.2
converted from NO by the DOC. Accordingly, one metric for
indicating the condition of the DOC 30 is the NO.sub.2/NOx ratio of
the exhaust gas exiting the DOC.
[0036] In addition to treating the hydrocarbon and CO
concentrations in the exhaust gas, the DOC 30 can also be used in
the controlled regeneration of the DPF 40 when present, the SCR
catalyst 50, and the AMOX catalyst 60. This can be accomplished
through the injection, or dosing, of unburned HC into the exhaust
gas upstream of the DOC 30. Upon contact with the DOC 30, the
unburned HC undergoes an exothermic oxidation reaction which leads
to an increase in the temperature of the exhaust gas exiting the
DOC 30 and subsequently entering the DPF 40, SCR catalyst 50,
and/or the AMOX catalyst 60. The amount of unburned HC added to the
exhaust gas is selected to achieve the desired temperature increase
or target controlled regeneration temperature.
[0037] When present, the DPF 40 can be any of various flow-through
designs known in the art, and configured to reduce particulate
matter concentrations, e.g., soot and ash, in the exhaust gas to
meet requisite emission standards. According to certain
applications, such as in emerging markets and developing countries,
the exhaust aftertreatment system 22 does not include a DPF 40.
Because such systems lack a DPF 40, particulate matter and other
constituents normally captured by a DPF are passed and accumulate
onto the SCR catalyst 50 and AMOX catalyst 60. Therefore, the need
for a more precisely controlled and robust system for estimating
the condition of components normally downstream of a DPF (e.g., the
SCR catalyst 50 and AMOX catalyst 60) and regenerating those
components when needed may be greater for systems without a DPF 40,
than those systems with a DPF. Additionally, the DPF 40 when
present may be configured to oxidize NO to form NO.sub.2
independent of the DOC 30.
[0038] As discussed above, the SCR system 52 includes a reductant
delivery system with a reductant (e.g., DEF) source 54, pump (not
shown) and delivery mechanism or doser 56. The reductant source 54
can be a container or tank capable of retaining a reductant, such
as, for example, ammonia (NH.sub.3), DEF (e.g., urea), or diesel
oil. The reductant source 54 is in reductant supplying
communication with the pump, which is configured to pump reductant
from the reductant source to the delivery mechanism 56 via a
reductant delivery line 58. The delivery mechanism 56 is positioned
upstream of the SCR catalyst 50. The delivery mechanism 56 is
selectively controllable to inject reductant directly into the
exhaust gas stream prior to entering the SCR catalyst 50.
[0039] In some embodiments, the reductant can either be ammonia or
DEF, which decomposes to produce ammonia. The ammonia reacts with
NOx in the presence of the SCR catalyst 50 to reduce the NOx to
less harmful emissions, such as N.sub.2 and H.sub.2O. The NOx in
the exhaust gas stream includes NO.sub.2 and NO. Generally, both
NO.sub.2 and NO are reduced to N.sub.2 and H.sub.2O through various
chemical reactions driven by the catalytic elements of the SCR
catalyst in the presence of NH.sub.3. However, as discussed above,
the chemical reduction of NO.sub.2 to N.sub.2 and H.sub.2O
typically is the most efficient chemical reaction. Therefore, in
general, the more NO.sub.2 in the exhaust gas stream compared to
NO, the more efficient the NO.sub.x reduction performed by the SCR
catalyst. Accordingly, the ability of the DOC 30 to convert NO to
NO.sub.2 directly affects the NOx reduction efficiency of the SCR
system 52. Put another way, the NOx reduction efficiency of the SCR
system 52 corresponds at least indirectly to the condition or
performance of the DOC 30. However, primarily, the NOx reduction
efficiency of the SCR system 52 corresponds with the condition or
performance of SCR catalyst 50.
[0040] The SCR catalyst 50 can be any of various catalysts known in
the art. For example, in some implementations, the SCR catalyst 50
is a vanadium-based catalyst, and in other implementations, the SCR
catalyst is a zeolite-based catalyst, such as a Cu-Zeolite or a
Fe-Zeolite catalyst. In one representative embodiment, the
reductant is aqueous urea and the SCR catalyst 50 is a
zeolite-based catalyst.
[0041] The AMOX catalyst 60 can be any of various flow-through
catalysts configured to react with ammonia to produce mainly
nitrogen. Generally, the AMOX catalyst 60 is utilized to remove
ammonia that has slipped through or exited the SCR catalyst 50
without reacting with NO.sub.x in the exhaust. In certain
instances, the aftertreatment system 22 can be operable with or
without an AMOX catalyst. Further, although the AMOX catalyst 60 is
shown as a separate unit from the SCR catalyst 50, in some
implementations, the AMOX catalyst can be integrated with the SCR
catalyst, e.g., the AMOX catalyst and the SCR catalyst can be
located within the same housing. The condition of the AMOX catalyst
60 can be represented by the performance of the AMOX catalyst
(i.e., the ability of the AMOX catalyst to convert ammonia into
mainly nitrogen).
[0042] Various sensors, such as temperature sensors 12 and mass
flow sensor 14, may be strategically disposed throughout the
exhaust aftertreatment system 22 and may be in communication with
the controller 100 to monitor operating conditions of the engine
system 10. In one embodiment, the temperature sensors 12 sense the
temperature of exhaust gas flowing through the exhaust
aftertreatment system 22 at various locations, and the mass flow
sensor 14 senses the rate at which the exhaust gas is flowing into
and through the exhaust aftertreatment system. Although only
temperature and mass flow sensors 12, 14 are shown, in other
embodiments, the engine system 10 and exhaust aftertreatment system
22 may include more or fewer sensors than those shown.
[0043] Although the exhaust aftertreatment system 22 shown includes
one of an DOC 30, an optional DPF 40, SCR catalyst 50, and AMOX
catalyst 60 positioned in specific locations relative to each other
along the exhaust flow path, in other embodiments, the exhaust
aftertreatment system may include more than one of any of the
various catalysts positioned in any of various positions relative
to each other along the exhaust flow path as desired. Further,
although the DOC 30 and AMOX catalyst 60 are non-selective
catalysts, in some embodiments, the DOC and AMOX catalyst can be
selective catalysts.
[0044] The controller 100 controls the operation of the engine
system 10 and associated sub-systems, such as the internal
combustion engine 20 and the exhaust gas aftertreatment system 22.
The controller 100 is depicted in FIGS. 1 and 2 as a single
physical unit, but can include two or more physically separated
units or components in some embodiments if desired. Generally, the
controller 100 receives multiple inputs, processes the inputs, and
transmits multiple outputs. The multiple inputs may include sensed
measurements, from the sensors, estimates from virtual sensors, and
various user inputs. For example, referring to FIG. 2, operating
conditions of the internal combustion engine 20 (e.g., engine
condition inputs 102), conditions of the exhaust gas (e.g., exhaust
condition inputs 104) flowing through the exhaust aftertreatment
system 22, and time condition inputs 106 can be ascertained from
any of the physical sensors, from any of various virtual sensors or
models, user input, and/or via the controller's 100 commands to the
engine, such as fuel rate, engine speed, engine load, and the like.
The inputs are processed by the controller 100 using various
algorithms, stored data, and other inputs to update the stored data
and/or generate output values. The generated output values and/or
commands are transmitted to other components of the controller
and/or to one or more elements of the engine system 10 to control
the system to achieve desired results, and more specifically,
achieve desired exhaust gas emissions, and component performance
and longevity.
[0045] Generally, the controller 100 includes various modules for
controlling the operation of the engine system 10. For example, the
controller 100 includes one or more modules for estimating
conditions of the exhaust aftertreatment components 30, 40, 50, 60
and controlling the regeneration of the components. As is known in
the art, the controller 100 and its various modular components may
comprise processor, memory, and interface modules that may be
fabricated of semiconductor gates on one or more semiconductor
substrates. Each semiconductor substrate may be packaged in one or
more semiconductor devices mounted on circuit cards. Connections
between the modules may be through semiconductor metal layers,
substrate-to-substrate wiring, or circuit card traces or wires
connecting the semiconductor devices.
[0046] Referring to FIG. 2, the controller 100 includes a sulfur
oxidation module 110 and a hydrocarbon oxidation module 120.
Generally, the sulfur and hydrocarbon oxidation modules 110, 120 of
the controller 100 receive inputs 102, 104, 106 and generate a
sulfur regeneration command 112 and hydrocarbon regeneration
command 122, respectively, based on at least one of the inputs.
When generated, the commands 112, 122 communicate regeneration
event parameters to the engine system 10. In response to the
commands 112, 122, various components or levers of the engine
system 10 are actuated to effectuate a regeneration event
corresponding to the regeneration vent parameters of the commands.
For example, the regeneration event parameters may include an
exhaust temperature parameter, an exhaust mass flow rate parameter,
and a timing parameter, the engine system 10 actuates internal or
external fuel dosing components to increase the exhaust temperature
and engine speed for a specified time in accordance with the
parameters. Once commanded, the regeneration events can be
effectuated using any of various techniques known in the art as
desired.
[0047] As shown in FIG. 3, the sulfur oxidation module 110 includes
a DOC sulfur module 130, an SCR sulfur module 150, an AMOX sulfur
module 170, and a sulfur regeneration arbitration module 190. Each
of the DOC sulfur, SCR sulfur, and AMOX sulfur modules 130, 150,
170 generate a respective sulfur regeneration request 140, 160, 180
if certain estimated conditions are met. The sulfur regeneration
requests 140, 160, 180 are received by the sulfur regeneration
arbitration module 190, which arbitrates between one or more sulfur
regeneration requests, and a timer-based regeneration request, to
generate the sulfur regeneration command 112. The sulfur
regeneration command 112 then represents the characteristics of the
winning regeneration request from the arbitration process.
[0048] The DOC sulfur module 130 of the sulfur oxidation module 110
includes a DOC sulfur storage module 132, DOC sulfur release module
134, DOC sulfur accumulation module 136, and DOC sulfur
regeneration module 138. The DOC sulfur storage module 132 is
configured to estimate the amount of sulfur being stored (e.g.,
adsorbed) on the DOC 30. As defined herein, sulfur can include any
of various sulfur compounds, such as, for example, SOx (e.g.,
SO.sub.2 and SO.sub.3), H.sub.2SO.sub.4, SOx on soot, and sulfates
of ammonia and copper. According to the illustrated embodiment, the
DOC sulfur storage module 132 estimates the amount or quantity of
sulfur being stored on the DOC based on various inputs, such as,
for example, the engine out sulfur (i.e., the quantity of sulfur in
the exhaust gas exiting the engine 20 and entering the DOC 30), the
temperature of the DOC, and the mass flow rate of exhaust gas into
the DOC. In certain implementations, the engine out sulfur is a
function of the fuel rate 124 (i.e., the rate of fuel entering and
being consumed by the engine 20), and the fuel sulfur 126 (i.e.,
the concentration of sulfur in the fuel being consumed). Generally,
the engine out sulfur can be expressed in terms of a volumetric or
part-per-minute flow rate and is equal to a percentage of the fuel
rate 124 multiplied by the fuel sulfur 126. The temperature of the
DOC 30 (e.g., the catalyst bed of the DOC) can be determined by the
DOC sulfur storage module 132 according to any of various
techniques, such as using estimation modules and/or physical
sensors. For example, the temperature of the DOC 30 can be
determined based on the difference between exhaust gas temperature
measurements taken by the temperature sensors 12 upstream and
downstream of the DOC. Additionally, or alternatively, the exhaust
aftertreatment system 22 may have a DOC mid-bed temperature sensor
that more directly detects the temperature of the DOC 30.
[0049] According to one embodiment, the quantity of sulfur being
stored on the DOC 30, which can be expressed as the rate of sulfur
being stored on the DOC, for a given engine out sulfur value, can
be obtained from a look-up table that is stored on the DOC sulfur
storage module 132 and includes predetermined sulfur storage rates
on the DOC 30 compared to DOC temperature values and exhaust mass
flow rate values. The DOC sulfur storage module 132 can include a
plurality of look-up tables each associated with a given engine out
sulfur value. Accordingly, once the temperature of the DOC 30 and
exhaust mass flow rate is determined or known, the sulfur storage
rate on the DOC estimated by the DOC sulfur storage module 132 is
the predetermined value in the look-up table (associated with the
determined engine out sulfur value) for the determined DOC
temperature and exhaust flow rate values. Generally, the sulfur
adsorption rate on components is lower at higher exhaust gas
temperatures. For engine out sulfur values between or outside those
corresponding with the look-up tables, interpolation or
extrapolation techniques can be utilized to estimate the DOC sulfur
storage rate.
[0050] The quantity of sulfur stored on the DOC 30 over a desired
time period, which can be represented by the time input 192, is
then estimated by the DOC sulfur storage module 132 by multiplying
the estimated DOC sulfur storage rate by the desired time period.
In certain implementations, the quantity of sulfur stored on the
DOC over the desired time period represents an estimate of the
newly stored sulfur, which can be added to a previous estimate of
the accumulation of sulfur on the DOC 30, as will be explained in
more detail below, to obtain a more accurate estimate of the
quantity of sulfur currently stored on the DOC.
[0051] The DOC sulfur release module 134 of the DOC sulfur module
130 is configured to estimate the DOC outlet sulfur 142 (i.e., the
amount or quantity of sulfur being released (e.g., desorbed) from
the DOC 30) based on various inputs, such as, for example, the
temperature of the DOC and the quantity of sulfur stored on the
DOC. Generally, the sulfur release rate from components is lower at
higher exhaust gas temperatures. The DOC sulfur release module 134
may estimate the temperature of the DOC 30 in the same or similar
manner as the DOC sulfur storage module 132, or simply utilize the
temperature of the DOC estimated by the DOC sulfur storage module.
Similarly, the quantity of sulfur stored on the DOC 30 can be
obtained from the DOC sulfur storage module 132 or can be based on
a previous estimate of the accumulation of sulfur on the DOC.
[0052] According to one embodiment, the DOC outlet sulfur 142 or
amount of sulfur being released from the DOC 30, which can be
expressed as the rate of sulfur being released from the DOC, can be
obtained from a look-up table that is stored on the DOC sulfur
release module 134 and includes predetermined sulfur release rates
from the DOC 30 compared to DOC temperature values and DOC sulfur
storage values. The DOC sulfur release module 134 can include a
plurality of look-up tables each associated with a given DOC outlet
sulfur value. Accordingly, once the temperature of the DOC 30 and
DOC outlet sulfur value is determined or known, the sulfur release
rate from the DOC estimated by the DOC sulfur release module 134 is
the predetermined value in the look-up table for the determined DOC
temperature and DOC sulfur storage values. The quantity of sulfur
released from the DOC 30 over a desired time period (e.g., the same
desired time period used by the DOC sulfur storage module 132 to
estimate the DOC sulfur storage), which also can be represented by
the time input 192, is then estimated by the DOC sulfur release
module 134 by multiplying the estimated DOC sulfur release rate by
the desired time period.
[0053] The quantity of sulfur stored on the DOC 30 estimated by the
DOC sulfur storage module 132 and the DOC outlet sulfur 142 (or
quantity of sulfur released from the DOC) estimated by the DOC
sulfur release module 134 is used by the DOC sulfur accumulation
module 136 to estimate a total accumulation of sulfur on the DOC
30. The DOC sulfur accumulation module 136 estimates the total
accumulation of sulfur on the DOC 30 based on a difference between
the estimated quantity of sulfur stored on the DOC 30 and the
estimated quantity of sulfur released from the DOC. In one
implementation, the DOC sulfur accumulation module 136 sets the
total accumulation of sulfur on the DOC 30 equal to the difference
between the estimated quantity of sulfur stored on the DOC 30 and
the estimated quantity of sulfur released from the DOC.
[0054] The DOC sulfur regeneration module 138 generates a DOC
sulfur regeneration request 140 based on a comparison between the
total accumulation of sulfur on the DOC 30 estimated by the DOC
sulfur accumulation module 136 and a DOC sulfur accumulation
threshold. In one embodiment, the DOC sulfur regeneration module
138 generates a DOC sulfur regeneration request 140 only when the
total accumulation of sulfur on the DOC 30 estimated by the DOC
sulfur accumulation module 136 meets (e.g., is equal to or exceeds)
the DOC sulfur accumulation threshold. In such an embodiment,
should the total accumulation of sulfur on the DOC 30 estimated by
the DOC sulfur accumulation module 136 not meet the DOC sulfur
accumulation threshold, then a DOC sulfur regeneration request 140
is not generated. The DOC sulfur regeneration request 140
represents a demand to regenerate the DOC 30 at specific
regeneration event operating parameters (e.g., exhaust temperature,
exhaust mass flow rate, and timing parameter). The operating
parameters of the DOC regeneration event demanded by the DOC sulfur
regeneration request 140 may vary based on any of various factors,
such as, for example, the total accumulation of sulfur on the DOC
30, the period of time since the last DOC regeneration event, and
the like. In some implementations, the sulfur regeneration request
140 is generated even if the total accumulation of sulfur on the
DOC 30 does not meet the DOC sulfur accumulation threshold.
However, in such implementations, the request 140 may be void of
regeneration event parameters, such that the request effectively
does not demand a regeneration event.
[0055] The DOC sulfur accumulation threshold corresponds with a DOC
performance threshold. Like described above, the accumulation of
sulfur on the DOC 30 may have a proportionally negative effect on
the performance of the DOC. For example, the greater the
accumulation of sulfur on the DOC 30, the lower the oxidation rate
of CO to CO.sub.2 and the lower the oxidation of NO to NO.sub.2.
Accordingly, the DOC sulfur accumulation threshold can be
predetermined to correspond with a minimum allowable performance
characteristic, such as a minimum allowable CO to CO.sub.2
oxidation rate or efficiency and/or minimum allowable NO to
NO.sub.2 oxidation rate or efficiency. As defined herein, allowable
may mean desirable. In this manner, the DOC sulfur regeneration
module 138 is configured to demand a DOC regeneration event by
generating the DOC sulfur regeneration request 140 before the
performance of the DOC 30 drops below the minimum allowable
performance characteristic.
[0056] Before a DOC regeneration event according to the DOC sulfur
regeneration request 140 is initiated, the DOC sulfur regeneration
request 140 is received by the sulfur regeneration arbitration
module 190, which determines whether the DOC sulfur regeneration
request has priority over other possible regeneration requests, as
will be described in more detail below. If the sulfur regeneration
arbitration module 190 determines that the DOC sulfur regeneration
request 140 has priority, then the sulfur regeneration arbitration
module generates a sulfur regeneration command 112 that corresponds
with the regeneration event parameters demanded by the DOC sulfur
regeneration request.
[0057] The SCR sulfur module 150 of the sulfur oxidation module 110
is configured in a manner analogous to the DOC sulfur module 130
except the SCR sulfur module applies to the SCR catalyst 50 instead
of the DOC 30. For example, the SCR sulfur module 150 includes an
SCR sulfur storage module 152, SCR sulfur release module 154, SCR
sulfur accumulation module 156, and SCR sulfur regeneration module
158. The SCR sulfur storage module 152 is configured to estimate
the amount of sulfur being stored on the SCR catalyst 50. According
to the illustrated embodiment, the SCR sulfur storage module 152
estimates the amount or quantity of sulfur being stored on the SCR
based on various inputs, such as, for example, the DOC outlet
sulfur 142 estimated by the DOC sulfur release module 134 (i.e.,
the quantity of sulfur in the exhaust gas exiting the DOC 30 and
entering the SCR catalyst 50), the temperature of the SCR catalyst
50, and the mass flow rate of exhaust gas into the SCR catalyst.
The temperature of the SCR catalyst 50 (e.g., the catalyst bed of
the SCR catalyst) can be determined by the SCR sulfur storage
module 152 according to any of various techniques, such as using
estimation modules and/or physical sensors. For example, the
temperature of the SCR catalyst 50 can be determined based on the
difference between exhaust gas temperature measurements taken by
the temperature sensors 12 upstream and downstream of the SCR
catalyst 50. Additionally, or alternatively, the exhaust
aftertreatment system 22 may have an SCR catalyst mid-bed
temperature sensor that more directly detects the temperature of
the SCR catalyst 50.
[0058] According to one embodiment, the quantity of sulfur being
stored on the SCR catalyst 50, which can be expressed as the rate
of sulfur being stored on the SCR catalyst 50, for a given DOC
outlet sulfur value 142, can be obtained from a look-up table that
is stored on the SCR sulfur storage module 152 and includes
predetermined sulfur storage rates on the SCR catalyst 50 compared
to SCR catalyst temperature values and exhaust mass flow rate
values. The SCR sulfur storage module 152 can include a plurality
of look-up tables each associated with a given DOC outlet sulfur
value 142. Accordingly, once the temperature of the SCR catalyst 50
and exhaust mass flow rate is determined or known, the sulfur
storage rate on the SCR catalyst estimated by the SCR sulfur
storage module 152 is the predetermined value in the look-up table
(associated with the determined DOC outlet sulfur value 142) for
the determined SCR catalyst temperature and exhaust flow rate
values. For DOC outlet sulfur values 142 between or outside those
corresponding with the look-up tables, interpolation or
extrapolation techniques can be utilized to estimate the SCR sulfur
storage rate.
[0059] The quantity of sulfur stored on the SCR catalyst 50 over a
desired time period, which can be represented by the time input
192, is then estimated by the SCR sulfur storage module 152 by
multiplying the estimated SCR sulfur storage rate by the desired
time period. In certain implementations, the quantity of sulfur
stored on the SCR catalyst 50 over the desired time period
represents an estimate of the newly stored sulfur on the SCR
catalyst, which can be added to a previous estimate of the
accumulation of sulfur on the SCR catalyst, as will be explained in
more detail below, to obtain a more accurate estimate of the
quantity of sulfur currently stored on the SCR catalyst.
[0060] The SCR sulfur release module 154 of the SCR sulfur module
150 is configured to estimate the SCR outlet sulfur 162 (i.e., the
amount or quantity of sulfur being released from the SCR catalyst
50) based on various inputs, such as, for example, the temperature
of the SCR catalyst and the quantity of sulfur stored on the SCR
catalyst. The SCR sulfur release module 154 may estimate the
temperature of the SCR catalyst 50 in the same or similar manner as
the SCR sulfur storage module 152, or simply utilize the
temperature of the SCR catalyst estimated by the SCR sulfur storage
module. Similarly, the quantity of sulfur stored on the SCR
catalyst 50 can be obtained from the SCR sulfur storage module 152
or can be based on a previous estimate of the accumulation of
sulfur on the SCR catalyst.
[0061] According to one embodiment, the SCR outlet sulfur 162 or
amount of sulfur being released from the SCR catalyst 50, which can
be expressed as the rate of sulfur being released from the SCR
catalyst, can be obtained from a look-up table that is stored on
the SCR sulfur release module 154 and includes predetermined sulfur
release rates from the SCR catalyst 50 compared to SCR catalyst
temperature values and SCR catalyst sulfur storage values. The SCR
sulfur release module 154 can include a plurality of look-up tables
each associated with a given SCR outlet sulfur value 162.
Accordingly, once the temperature of the SCR catalyst 50 and SCR
outlet sulfur value 162 is determined or known, the sulfur release
rate from the SCR catalyst 50 estimated by the SCR sulfur release
module 154 is the predetermined value in the look-up table for the
determined SCR temperature and SCR sulfur storage values. The
quantity of sulfur released from the SCR catalyst 50 over a desired
time period (e.g., the same desired time period used by the SCR
sulfur storage module 152 to estimate the SCR sulfur storage),
which also can be represented by the time input 192, is then
estimated by the SCR sulfur release module 154 by multiplying the
estimated SCR sulfur release rate by the desired time period.
[0062] The quantity of sulfur stored on the SCR catalyst 50
estimated by the SCR sulfur storage module 152 and the SCR outlet
sulfur 162 (or quantity of sulfur released from the SCR catalyst)
estimated by the SCR sulfur release module 154 is used by the SCR
sulfur accumulation module 156 to estimate a total accumulation of
sulfur on the SCR catalyst 50. The SCR sulfur accumulation module
156 estimates the total accumulation of sulfur on the SCR catalyst
50 based on a difference between the estimated quantity of sulfur
stored on the SCR catalyst 50 and the estimated quantity of sulfur
released from the SCR catalyst. In one implementation, the SCR
sulfur accumulation module 156 sets the total accumulation of
sulfur on the SCR catalyst 50 equal to the difference between the
estimated quantity of sulfur stored on the SCR catalyst and the
estimated quantity of sulfur released from the SCR catalyst.
[0063] The SCR sulfur regeneration module 158 generates an SCR
sulfur regeneration request 160 based on a comparison between the
total accumulation of sulfur on the SCR catalyst 50 estimated by
the SCR sulfur accumulation module 156 and an SCR sulfur
accumulation threshold. In one embodiment, the SCR sulfur
regeneration module 158 generates an SCR sulfur regeneration
request 160 only when the total accumulation of sulfur on the SCR
catalyst 50 estimated by the SCR sulfur accumulation module 156
meets (e.g., is equal to or exceeds) the SCR sulfur accumulation
threshold. In such an embodiment, should the total accumulation of
sulfur on the SCR catalyst 50 estimated by the SCR sulfur
accumulation module 156 not meet the SCR sulfur accumulation
threshold, then an SCR sulfur regeneration request 160 is not
generated. The SCR sulfur regeneration request 160 represents a
demand to regenerate the SCR catalyst 50 at specific regeneration
event operating parameters (e.g., exhaust temperature, exhaust mass
flow rate, and timing parameter). The operating parameters of the
SCR catalyst regeneration event demanded by the SCR sulfur
regeneration request 160 may vary based on any of various factors,
such as, for example, the total accumulation of sulfur on the SCR
catalyst 50, the period of time since the last SCR catalyst
regeneration event, and the like. In some implementations, the
sulfur regeneration request 160 is generated even if the total
accumulation of sulfur on the SCR catalyst 50 does not meet the SCR
sulfur accumulation threshold. However, in such implementations,
the request 160 may be void of regeneration event parameters, such
that the request effectively does not demand a regeneration
event.
[0064] The SCR sulfur accumulation threshold corresponds with an
SCR catalyst performance threshold. Like described above, the
accumulation of sulfur on the SCR catalyst 50 may have a
proportionally negative effect on the performance of the SCR
catalyst. For example, the greater the accumulation of sulfur on
the SCR catalyst 50, the lower the conversion rate of NOx in the
presence of ammonia or the lower the NOx conversion efficiency.
Accordingly, the SCR sulfur accumulation threshold can be
predetermined to correspond with a minimum allowable performance
characteristic, such as a minimum allowable NOx conversion rate or
efficiency. In this manner, the SCR sulfur regeneration module 158
is configured to demand an SCR catalyst regeneration event by
generating the SCR sulfur regeneration request 160 before the
performance of the SCR catalyst 50 drops below the minimum
allowable performance characteristic. Because the performance
characteristics of the DOC 30 are different than those of the SCR
catalyst 50, the respective sulfur accumulation thresholds can be
different. For example, in certain implementations, the performance
of the DOC 30 may better tolerate sulfur accumulations than the SCR
catalyst 50. Accordingly, in such implementations, the sulfur
accumulation threshold of the DOC 30 may be higher than that of the
SCR catalyst 50. In AMOX other implementations, the sulfur
accumulation threshold of the DOC 30 may be lower than that of the
SCR catalyst 50.
[0065] Before an SCR catalyst regeneration event according to the
SCR sulfur regeneration request 160 is initiated, the SCR sulfur
regeneration request is received by the sulfur regeneration
arbitration module 190, which determines whether the SCR sulfur
regeneration request has priority over other possible regeneration
requests, such as the DOC sulfur regeneration request 140 or other
requests as will be described in more detail below. If the sulfur
regeneration arbitration module 190 determines that the SCR sulfur
regeneration request 160 has priority, then the sulfur regeneration
arbitration module generates a sulfur regeneration command 112 that
corresponds with the regeneration event parameters demanded by the
SCR sulfur regeneration request.
[0066] The AMOX sulfur module 170 of the sulfur oxidation module
110 is configured in a manner analogous to the DOC and SCR sulfur
modules 130, 150 except the AMOX sulfur module applies to the AMOX
catalyst 60 instead of the DOC 30 and SCR catalyst 50. For example,
the AMOX sulfur module 170 includes an AMOX sulfur storage module
172, AMOX sulfur release module 174, AMOX sulfur accumulation
module 176, and AMOX sulfur regeneration module 178. The AMOX
sulfur storage module 172 is configured to estimate the amount of
sulfur being stored on the AMOX catalyst 60. According to the
illustrated embodiment, the AMOX sulfur storage module 172
estimates the amount or quantity of sulfur being stored on the AMOX
based on various inputs, such as, for example, the SCR outlet
sulfur 162 estimated by the SCR sulfur release module 154 (i.e.,
the quantity of sulfur in the exhaust gas exiting the SCR catalyst
50 and entering the AMOX catalyst 60), the temperature of the AMOX
catalyst 60, and the mass flow rate of exhaust gas into the AMOX
catalyst. The temperature of the AMOX catalyst 60 (e.g., the
catalyst bed of the AMOX catalyst) can be determined by the AMOX
sulfur storage module 172 according to any of various techniques,
such as using estimation modules and/or physical sensors. For
example, the temperature of the AMOX catalyst 60 can be determined
based on the difference between exhaust gas temperature
measurements taken by the temperature sensors 12 upstream and
downstream of the AMOX catalyst 60. Additionally, or alternatively,
the exhaust aftertreatment system 22 may have an AMOX catalyst
mid-bed temperature sensor that more directly detects the
temperature of the AMOX catalyst 60.
[0067] According to one embodiment, the quantity of sulfur being
stored on the AMOX catalyst 60, which can be expressed as the rate
of sulfur being stored on the AMOX catalyst, for a given SCR outlet
sulfur value 162, can be obtained from a look-up table that is
stored on the AMOX sulfur storage module 172 and includes
predetermined sulfur storage rates on the AMOX catalyst 60 compared
to AMOX catalyst temperature values and exhaust mass flow rate
values. The AMOX sulfur storage module 172 can include a plurality
of look-up tables each associated with a given SCR outlet sulfur
value 162. Accordingly, once the temperature of the AMOX catalyst
60 and exhaust mass flow rate is determined or known, the sulfur
storage rate on the AMOX catalyst estimated by the AMOX sulfur
storage module 172 is the predetermined value in the look-up table
(associated with the determined SCR outlet sulfur value 162) for
the determined AMOX catalyst temperature and exhaust flow rate
values. For SCR outlet sulfur values 162 between or outside those
corresponding with the look-up tables, interpolation or
extrapolation techniques can be utilized to estimate the AMOX
sulfur storage rate.
[0068] The quantity of sulfur stored on the AMOX catalyst 60 over a
desired time period, which can be represented by the time input
192, is then estimated by the AMOX sulfur storage module 172 by
multiplying the estimated AMOX sulfur storage rate by the desired
time period. In certain implementations, the quantity of sulfur
stored on the AMOX catalyst 60 over the desired time period
represents an estimate of the newly stored sulfur on the AMOX
catalyst, which can be added to a previous estimate of the
accumulation of sulfur on the AMOX catalyst, as will be explained
in more detail below, to obtain a more accurate estimate of the
quantity of sulfur currently stored on the AMOX catalyst.
[0069] The AMOX sulfur release module 174 of the AMOX sulfur module
170 is configured to estimate the AMOX outlet sulfur 182 (i.e., the
amount or quantity of sulfur being released from the AMOX catalyst
60) based on various inputs, such as, for example, the temperature
of the AMOX catalyst and the quantity of sulfur stored on the AMOX
catalyst. The AMOX sulfur release module 174 may estimate the
temperature of the AMOX catalyst 60 in the same or similar manner
as the AMOX sulfur storage module 172, or simply utilize the
temperature of the AMOX catalyst estimated by the AMOX sulfur
storage module. Similarly, the quantity of sulfur stored on the
AMOX catalyst 60 can be obtained from the AMOX sulfur storage
module 172 or can be based on a previous estimate of the
accumulation of sulfur on the AMOX catalyst 60.
[0070] According to one embodiment, the AMOX outlet sulfur 182 or
amount of sulfur being released from the AMOX catalyst 60, which
can be expressed as the rate of sulfur being released from the AMOX
catalyst, can be obtained from a look-up table that is stored on
the AMOX sulfur release module 174 and includes predetermined
sulfur release rates from the AMOX catalyst 60 compared to AMOX
catalyst temperature values and AMOX catalyst sulfur storage
values. The AMOX sulfur release module 174 can include a plurality
of look-up tables each associated with a given AMOX outlet sulfur
value 182. Accordingly, once the temperature of the AMOX catalyst
60 and AMOX outlet sulfur value 182 is determined or known, the
sulfur release rate from the AMOX catalyst 60 estimated by the AMOX
sulfur release module 174 is the predetermined value in the look-up
table for the determined AMOX temperature and AMOX sulfur storage
values. The quantity of sulfur released from the AMOX catalyst 60
over a desired time period (e.g., the same desired time period used
by the AMOX sulfur storage module 172 to estimate the AMOX sulfur
storage), which also can be represented by the time input 192, is
then estimated by the AMOX sulfur release module 174 by multiplying
the estimated AMOX sulfur release rate by the desired time
period.
[0071] The quantity of sulfur stored on the AMOX catalyst 60
estimated by the AMOX sulfur storage module 172 and the AMOX outlet
sulfur 182 (or quantity of sulfur released from the AMOX catalyst)
estimated by the AMOX sulfur release module 174 is used by the AMOX
sulfur accumulation module 176 to estimate a total accumulation of
sulfur on the AMOX catalyst 60. The AMOX sulfur accumulation module
176 estimates the total accumulation of sulfur on the AMOX catalyst
60 based on a difference between the estimated quantity of sulfur
stored on the AMOX catalyst 60 and the estimated quantity of sulfur
released from the AMOX catalyst. In one implementation, the AMOX
sulfur accumulation module 176 sets the total accumulation of
sulfur on the AMOX catalyst 60 equal to the difference between the
estimated quantity of sulfur stored on the AMOX catalyst and the
estimated quantity of sulfur released from the AMOX catalyst.
[0072] The AMOX sulfur regeneration module 178 generates an AMOX
sulfur regeneration request 180 based on a comparison between the
total accumulation of sulfur on the AMOX catalyst 60 estimated by
the AMOX sulfur accumulation module 176 and an AMOX sulfur
accumulation threshold. In one embodiment, the AMOX sulfur
regeneration module 178 generates an AMOX sulfur regeneration
request 180 only when the total accumulation of sulfur on the AMOX
catalyst 60 estimated by the AMOX sulfur accumulation module 176
meets (e.g., is equal to or exceeds) the AMOX sulfur accumulation
threshold. In such an embodiment, should the total accumulation of
sulfur on the AMOX catalyst 60 estimated by the AMOX sulfur
accumulation module 176 not meet the AMOX sulfur accumulation
threshold, then an AMOX sulfur regeneration request 180 is not
generated. The AMOX sulfur regeneration request 180 represents a
demand to regenerate the AMOX catalyst 60 at specific regeneration
event operating parameters (e.g., exhaust temperature, exhaust mass
flow rate, and timing parameter). The operating parameters of the
AMOX catalyst regeneration event demanded by the AMOX sulfur
regeneration request 180 may vary based on any of various factors,
such as, for example, the total accumulation of sulfur on the AMOX
catalyst 60, the period of time since the last AMOX catalyst
regeneration event, and the like. In some implementations, the
sulfur regeneration request 180 is generated even if the total
accumulation of sulfur on the AMOX catalyst 60 does not meet the
AMOX sulfur accumulation threshold. However, in such
implementations, the request 180 may be void of regeneration event
parameters, such that the request effectively does not demand a
regeneration event.
[0073] The AMOX sulfur accumulation threshold corresponds with an
AMOX catalyst performance threshold. Like described above, the
accumulation of sulfur on the AMOX catalyst 60 may have a
proportionally negative effect on the performance of the AMOX
catalyst. For example, the greater the accumulation of sulfur on
the AMOX catalyst 60, the lower the conversion rate of ammonia or
the lower the ammonia conversion efficiency. Accordingly, the AMOX
sulfur accumulation threshold can be predetermined to correspond
with a minimum allowable performance characteristic, such as a
minimum allowable ammonia oxidation rate or efficiency. In this
manner, the AMOX sulfur regeneration module 178 is configured to
demand an AMOX catalyst regeneration event by generating the SCR
sulfur regeneration request 180 before the performance of the AMOX
catalyst 60 drops below the minimum allowable performance
characteristic. Because the performance characteristics of the DOC
30 and SCR catalyst 50 are different than those of the AMOX
catalyst 60, the respective sulfur accumulation thresholds can be
different. For example, in certain implementations, the performance
of the DOC 30 and/or SCR catalyst 50 may better tolerate sulfur
accumulations than the AMOX catalyst 60. Accordingly, in such
implementations, the sulfur accumulation thresholds of the DOC 30
and/or SCR catalyst 50 may be higher than that of the AMOX catalyst
60. In other implementations, the sulfur accumulation threshold of
the DOC 30 and/or SCR catalyst 50 may be lower than that of the
AMOX catalyst 60.
[0074] Before an AMOX catalyst regeneration event according to the
AMOX sulfur regeneration request 180 is initiated, the AMOX sulfur
regeneration request is received by the sulfur regeneration
arbitration module 190, which determines whether the AMOX sulfur
regeneration request has priority over other possible regeneration
requests, such as the DOC sulfur regeneration request 140, SCR
sulfur regeneration request 160, or other requests as will be
described in more detail below. If the sulfur regeneration
arbitration module 190 determines that the AMOX sulfur regeneration
request 180 has priority, then the sulfur regeneration arbitration
module generates a sulfur regeneration command 112 that corresponds
with the regeneration event parameters demanded by the AMOX sulfur
regeneration request.
[0075] The sulfur regeneration arbitration module 190 may include a
time-based regeneration module or algorithm configured to request a
system regeneration event of the exhaust aftertreatment system 22
based on the passing of a preset period of time since the last
regeneration event, which may be associated with a predetermined
amount of fuel consumed by the engine 20. Accordingly, the sulfur
regeneration module 190 monitors the initiation and completion of
regeneration events of the exhaust aftertreatment system 22, and
monitors the amount of time since the completion of the latest
regeneration event. The time since the latent regeneration event
can be determined from the time input 192, which can be tied to an
internal timer device of the controller 100 or external timer
device in communication with the controller. When the preset time
has been reached, the time-based regeneration module of the sulfur
regeneration arbitration module 190 generates a time-based sulfur
regeneration request that demands a regeneration of the exhaust
aftertreatment system 22 at specific regeneration event operating
parameters (e.g., exhaust temperature, exhaust mass flow rate, and
timing parameter). The sulfur regeneration arbitration module 190
determines whether the time-based sulfur regeneration request has
priority over other possible regeneration requests. If the sulfur
regeneration arbitration module 190 determines that the time-based
sulfur regeneration request has priority, then the sulfur
regeneration arbitration module generates a sulfur regeneration
command 112 that corresponds with the regeneration event parameters
demanded by the time-based sulfur regeneration request.
[0076] The sulfur regeneration arbitration module 190 may include
any of various arbitration schemes for determining which of a
plurality of regeneration requests has priority. Such arbitration
schemes may take into account precalibrated regeneration timers,
system efficiency monitors, and accumulation thresholds that are
set based on the impact of sulfur on the performance and emissions
behavior of one or more of the aftertreatment components of the
system 22. For example, the winning request could represent the
component that is most severely impacted by sulfur effects if the
precalibrated timer has not timed-out and the system efficiency is
still normal.
[0077] The regeneration event parameters demanded by the DOC, SCR,
AMOX, and time-based sulfur regeneration requests can be different.
For example, one request may demand a shorter regeneration event
that is sufficient to clean sulfur from a corresponding component,
but insufficient to clean sulfur from another component. Or, as
another example, one request may demand a regeneration event with a
lower exhaust gas temperature that is sufficient to clean sulfur
from a corresponding component, but insufficient to clean sulfur
from another component. To account for such discrepancies, the
sulfur modules 130, 150, 170 of the sulfur oxidation module 110
continue to operate as described above during a regeneration event
to continuously monitor the storage, release, and accumulation of
sulfur on the components while regeneration events are occurring,
even if the regeneration event was triggered for a single
component. For example, the extra sulfur being released from the
DOC 30 during a regeneration event is accounted for in the
calculation of the DOC outlet sulfur 142 as extra sulfur being
introduced into the SCR catalyst 50. In this manner, an accurate
and current estimate of the sulfur accumulation status for each
component is known before, during, and after any regeneration
event.
[0078] As shown in FIG. 4, the hydrocarbon (HC) oxidation module
120 includes a DOC HC module 230, an SCR HC module 250, an AMOX HC
module 270, and a HC regeneration arbitration module 290 each
similar to the DOC sulfur module 130, an SCR sulfur module 150, an
AMOX sulfur module 170, and a sulfur regeneration arbitration
module 190, but configured for HC accumulation and removal instead
of sulfur accumulation and removal. Each of the DOC HC, SCR HC, and
AMOX HC modules 230, 250, 270 generates a respective HC
regeneration request 240, 260, 280 if certain estimated conditions
are met. The HC regeneration requests 240, 260, 280 are received by
the HC regeneration arbitration module 290, which arbitrates
between one or more HC regeneration requests, and a timer-based
regeneration request, to generate the HC regeneration command 122.
The HC regeneration command 122 then represents the characteristics
of the winning regeneration request from the arbitration
process.
[0079] The DOC HC module 230 of the HC oxidation module 120
includes a DOC HC storage module 232, DOC HC release module 234,
DOC HC accumulation module 236, and DOC HC regeneration module 238.
The DOC HC storage module 232 is configured to estimate the amount
of HC being stored on the DOC 30. According to the illustrated
embodiment, the DOC HC storage module 232 estimates the amount or
quantity of HC being stored on the DOC based on various inputs,
such as, for example, the engine out HC 224 (i.e., the quantity of
HC in the exhaust gas exiting the engine 20 and entering the DOC
30). In certain implementations, the engine out HC is a function of
the fuel rate 124 (i.e., the rate of fuel entering and being
consumed by the engine 20). Generally, the engine out HC can be
expressed in terms of a volumetric or part-per-minute flow rate.
The temperature of the DOC 30 can be determined in a manner similar
to that described above.
[0080] According to one embodiment, the quantity of HC being stored
on the DOC 30, which can be expressed as the rate of HC being
stored on the DOC, for a given engine out HC value 224, can be
obtained from a look-up table that is stored on the DOC HC storage
module 232 and includes predetermined HC storage rates on the DOC
30 compared to DOC temperature values and exhaust mass flow rate
values. The DOC HC storage module 232 can include a plurality of
look-up tables each associated with a given engine out HC value
224. Accordingly, once the temperature of the DOC 30 and exhaust
mass flow rate is determined or known, the HC storage rate on the
DOC estimated by the DOC HC storage module 232 is the predetermined
value in the look-up table (associated with the determined engine
out HC value) for the determined DOC temperature and exhaust flow
rate values. Generally, the HC adsorption rate on components is
lower at higher exhaust gas temperatures. For engine out HC values
between or outside those corresponding with the look-up tables,
interpolation or extrapolation techniques can be utilized to
estimate the DOC HC storage rate.
[0081] The quantity of HC stored on the DOC 30 over a desired time
period, which can be represented by the time input 192, is then
estimated by the DOC HC storage module 232 by multiplying the
estimated DOC HC storage rate by the desired time period. In
certain implementations, the quantity of HC stored on the DOC over
the desired time period represents an estimate of the newly stored
HC, which can be added to a previous estimate of the accumulation
of HC on the DOC 30, as will be explained in more detail below, to
obtain a more accurate estimate of the quantity of HC currently
stored on the DOC.
[0082] The DOC HC release module 234 of the DOC HC module 230 is
configured to estimate the DOC outlet HC 242 (i.e., the amount or
quantity of HC being released from the DOC 30) based on various
inputs, such as, for example, the temperature of the DOC and the
quantity of HC stored on the DOC. Generally, the HC release rate
from components is lower at higher exhaust gas temperatures. The
DOC HC release module 234 may estimate the temperature of the DOC
30 in the same or similar manner as the DOC HC storage module 232,
or simply utilize the temperature of the DOC estimated by the DOC
HC storage module. Similarly, the quantity of HC stored on the DOC
30 can be obtained from the DOC HC storage module 232 or can be
based on a previous estimate of the accumulation of HC on the
DOC.
[0083] According to one embodiment, the DOC outlet HC 242 or amount
of HC being released from the DOC 30, which can be expressed as the
rate of HC being released from the DOC, can be obtained from a
look-up table that is stored on the DOC HC release module 234 and
includes predetermined HC release rates from the DOC 30 compared to
DOC temperature values and DOC HC storage values. The DOC HC
release module 234 can include a plurality of look-up tables each
associated with a given DOC outlet HC value. Accordingly, once the
temperature of the DOC 30 and DOC outlet HC value is determined or
known, the HC release rate from the DOC estimated by the DOC HC
release module 234 is the predetermined value in the look-up table
for the determined DOC temperature and DOC HC storage values. The
quantity of HC released from the DOC 30 over a desired time period
(e.g., the same desired time period used by the DOC HC storage
module 232 to estimate the DOC HC storage), which also can be
represented by the time input 192, is then estimated by the DOC HC
release module 234 by multiplying the estimated DOC HC release rate
by the desired time period.
[0084] The quantity of HC stored on the DOC 30 estimated by the DOC
storage module 232 and the DOC outlet HC 242 (or quantity of HC
released from the DOC) estimated by the DOC HC release module 234
is used by the DOC HC accumulation module 236 to estimate a total
accumulation of HC on the DOC 30. The DOC HC accumulation module
236 estimates the total accumulation of HC on the DOC 30 based on a
difference between the estimated quantity of HC stored on the DOC
30 and the estimated quantity of HC released from the DOC. In one
implementation, the DOC HC accumulation module 236 sets the total
accumulation of HC on the DOC 30 equal to the difference between
the estimated quantity of HC stored on the DOC 30 and the estimated
quantity of HC released from the DOC.
[0085] The DOC HC regeneration module 238 generates a DOC HC
regeneration request 240 based on a comparison between the total
accumulation of HC on the DOC 30 estimated by the DOC HC
accumulation module 236 and a DOC HC accumulation threshold. In one
embodiment, the DOC HC regeneration module 238 generates a DOC HC
regeneration request 240 only when the total accumulation of HC on
the DOC 30 estimated by the DOC HC accumulation module 236 meets
(e.g., is equal to or exceeds) the DOC HC accumulation threshold
(or other condition thresholds are met). In such an embodiment,
should the total accumulation of HC on the DOC 30 estimated by the
DOC HC accumulation module 236 not meet the DOC HC accumulation
threshold, then a DOC HC regeneration request 240 is not generated.
The DOC HC regeneration request 240 represents a demand to
regenerate the DOC 30 at specific regeneration event operating
parameters (e.g., exhaust temperature, exhaust mass flow rate, and
timing parameter). The operating parameters of the DOC regeneration
event demanded by the DOC HC regeneration request 240 may vary
based on any of various factors, such as, for example, the total
accumulation of HC on the DOC 30, the period of time since the last
DOC regeneration event, and the like. In some implementations, the
HC regeneration request 240 is generated even if the total
accumulation of HC on the DOC 30 does not meet the DOC HC
accumulation threshold. However, in such implementations, the
request 140 may be void of regeneration event parameters, such that
the request effectively does not demand a regeneration event.
[0086] The DOC HC accumulation threshold corresponds with a DOC
performance threshold. Like described above, the accumulation of HC
on the DOC 30 may have a proportionally negative effect on the
performance of the DOC. For example, the greater the accumulation
of HC on the DOC 30, the lower the oxidation rate of CO to CO.sub.2
and the lower the oxidation of NO to NO.sub.2. Accordingly, the DOC
HC accumulation threshold can be predetermined to correspond with a
minimum allowable performance characteristic, such as a minimum
allowable CO to CO.sub.2 oxidation rate and/or minimum allowable NO
to NO.sub.2 oxidation rate. In this manner, the DOC HC regeneration
module 238 is configured to demand a DOC regeneration event by
generating the DOC HC regeneration request 240 before the
performance of the DOC 30 drops below the minimum allowable
performance characteristic.
[0087] According to certain embodiments, the DOC HC regeneration
module 238 may include an exothermal module 244 that is configured
to monitor the exothermal conditions of the DOC 30, which include
the heat generation of the DOC. The DOC HC regeneration module 238
compares the exothermal conditions of the DOC 30 against
predetermined thresholds and generates a DOC HC regeneration
request 240 when the exothermal conditions meet the associated
thresholds. In one embodiment, an exothermal condition is a heat
generation rate of the DOC 30, and an exothermal condition
threshold is a maximum heat generation rate of the DOC. The maximum
heat generation rate of the DOC 30 may be associated with a rate
above which an uncontrolled or runaway regeneration of the DOC may
occur. Alternatively, the exothermal condition is an amount of heat
generated by the DOC 30, and the exothermal condition threshold is
a maximum allowable amount of heat generated by the DOC. The
maximum allowable amount of heat generated by the DOC 30 may be
associated with a heat generation value above which an uncontrolled
or runaway regeneration of the DOC may occur.
[0088] Uncontrolled or runaway regenerations can be mitigated by
performing a controlled regeneration of the DOC 30. Accordingly,
the DOC HC regeneration module 238 is configured to generate a DOC
HC regeneration request 240, which can be considered an exothermal
regeneration request under such circumstances, demanding a
regeneration event when the exothermal condition meets the
exothermal condition threshold, or before an uncontrolled or
runaway regeneration event occurs. The parameters of the
regeneration event demanded by a DOC HC regeneration request 240
generated from an exothermal condition threshold being met may be
different than a DOC HC regeneration request generated from an
estimated total HC accumulation on the DOC meeting a DOC HC
accumulation threshold.
[0089] Before a DOC regeneration event according to the DOC HC
regeneration request 240 is initiated, the DOC HC regeneration
request is received by the HC regeneration arbitration module 290,
which determines whether the DOC HC regeneration request has
priority over other possible regeneration requests, as will be
described in more detail below. If the HC regeneration arbitration
module 290 determines that the DOC HC regeneration request 240 has
priority, then the HC regeneration arbitration module generates a
HC regeneration command 122 that corresponds with the regeneration
event parameters demanded by the DOC HC regeneration request.
[0090] The SCR HC module 250 of the HC oxidation module 120 is
configured in a manner analogous to the DOC HC module 230 except
the SCR HC module applies to the SCR catalyst 50 instead of the DOC
30. For example, the SCR HC module 250 includes an SCR HC storage
module 252, SCR HC release module 254, SCR HC accumulation module
256, and SCR HC regeneration module 258. The SCR HC storage module
252 is configured to estimate the amount of HC being stored on the
SCR catalyst 50. According to the illustrated embodiment, the SCR
HC storage module 252 estimates the amount or quantity of HC being
stored on the SCR based on various inputs, such as, for example,
the DOC outlet HC 242 estimated by the DOC HC release module 234
(i.e., the quantity of HC in the exhaust gas exiting the DOC 30 and
entering the SCR catalyst 50), the temperature of the SCR catalyst
50, and the mass flow rate of exhaust gas into the SCR catalyst.
The temperature of the SCR catalyst 50 can be determined by the SCR
HC storage module 252 according to any of various techniques as
discussed above.
[0091] According to one embodiment, the quantity of HC being stored
on the SCR catalyst 50, which can be expressed as the rate of HC
being stored on the SCR catalyst 50, for a given DOC outlet HC
value 242, can be obtained from a look-up table that is stored on
the SCR HC storage module 252 and includes predetermined HC storage
rates on the SCR catalyst 50 compared to SCR catalyst temperature
values and exhaust mass flow rate values. The SCR HC storage module
252 can include a plurality of look-up tables each associated with
a given DOC outlet HC value 242. Accordingly, once the temperature
of the SCR catalyst 50 and exhaust mass flow rate is determined or
known, the HC storage rate on the SCR catalyst estimated by the SCR
HC storage module 252 is the predetermined value in the look-up
table (associated with the determined DOC outlet HC value 242) for
the determined SCR catalyst temperature and exhaust flow rate
values. For DOC outlet HC values 242 between or outside those
corresponding with the look-up tables, interpolation or
extrapolation techniques can be utilized to estimate the SCR HC
storage rate.
[0092] The quantity of HC stored on the SCR catalyst 50 over a
desired time period, which can be represented by the time input
192, is then estimated by the SCR HC storage module 252 by
multiplying the estimated SCR HC storage rate by the desired time
period. In certain implementations, the quantity of HC stored on
the SCR catalyst 50 over the desired time period represents an
estimate of the newly stored HC on the SCR catalyst, which can be
added to a previous estimate of the accumulation of HC on the SCR
catalyst, as will be explained in more detail below, to obtain a
more accurate estimate of the quantity of HC currently stored on
the SCR catalyst.
[0093] The SCR HC release module 254 of the SCR HC module 250 is
configured to estimate the SCR outlet HC 262 (i.e., the amount or
quantity of HC being released from the SCR catalyst 50) based on
various inputs, such as, for example, the temperature of the SCR
catalyst and the quantity of HC stored on the SCR catalyst. The SCR
HC release module 254 may estimate the temperature of the SCR
catalyst 50 in the same or similar manner as the SCR HC storage
module 252, or simply utilize the temperature of the SCR catalyst
estimated by the SCR HC storage module. Similarly, the quantity of
HC stored on the SCR catalyst 50 can be obtained from the SCR HC
storage module 252 or can be based on a previous estimate of the
accumulation of HC on the SCR catalyst.
[0094] According to one embodiment, the SCR outlet HC 262 or amount
of HC being released from the SCR catalyst 50, which can be
expressed as the rate of HC being released from the SCR catalyst,
can be obtained from a look-up table that is stored on the SCR HC
release module 254 and includes predetermined HC release rates from
the SCR catalyst 50 compared to SCR catalyst temperature values and
SCR catalyst HC storage values. The SCR HC release module 254 can
include a plurality of look-up tables each associated with a given
SCR outlet HC value 262. Accordingly, once the temperature of the
SCR catalyst 50 and SCR outlet HC value 262 is determined or known,
the HC release rate from the SCR catalyst 50 estimated by the SCR
HC release module 254 is the predetermined value in the look-up
table for the determined SCR temperature and SCR HC storage values.
The quantity of HC released from the SCR catalyst 50 over a desired
time period (e.g., the same desired time period used by the SCR HC
storage module 252 to estimate the SCR HC storage), which also can
be represented by the time input 192, is then estimated by the SCR
HC release module 254 by multiplying the estimated SCR HC release
rate by the desired time period.
[0095] The quantity of HC stored on the SCR catalyst 50 estimated
by the SCR HC storage module 252 and the SCR outlet HC 262 (or
quantity of HC released from the SCR catalyst) estimated by the SCR
HC release module 254 is used by the SCR HC accumulation module 256
to estimate a total accumulation of HC on the SCR catalyst 50. The
SCR HC accumulation module 256 estimates the total accumulation of
HC on the SCR catalyst 50 based on a difference between the
estimated quantity of HC stored on the SCR catalyst 50 and the
estimated quantity of HC released from the SCR catalyst. In one
implementation, the SCR HC accumulation module 256 sets the total
accumulation of HC on the SCR catalyst 50 equal to the difference
between the estimated quantity of HC stored on the SCR catalyst and
the estimated quantity of HC released from the SCR catalyst.
[0096] The SCR HC regeneration module 258 generates an SCR HC
regeneration request 260 based on a comparison between the total
accumulation of HC on the SCR catalyst 50 estimated by the SCR HC
accumulation module 256 and an SCR HC accumulation threshold. In
one embodiment, the SCR HC regeneration module 258 generates an SCR
HC regeneration request 260 only when the total accumulation of HC
on the SCR catalyst 50 estimated by the SCR HC accumulation module
256 meets (e.g., is equal to or exceeds) the SCR HC accumulation
threshold. In such an embodiment, should the total accumulation of
HC on the SCR catalyst 50 estimated by the SCR HC accumulation
module 256 not meet the SCR HC accumulation threshold, then an SCR
HC regeneration request 260 is not generated. The SCR HC
regeneration request 260 represents a demand to regenerate the SCR
catalyst 50 at specific regeneration event operating parameters
(e.g., exhaust temperature, exhaust mass flow rate, and timing
parameter). The operating parameters of the SCR catalyst
regeneration event demanded by the SCR HC regeneration request 260
may vary based on any of various factors, such as, for example, the
total accumulation of HC on the SCR catalyst 50, the period of time
since the last SCR catalyst regeneration event, and the like. In
some implementations, the HC regeneration request 260 is generated
even if the total accumulation of HC on the SCR catalyst 50 does
not meet the SCR HC accumulation threshold. However, in such
implementations, the request 260 may be void of regeneration event
parameters, such that the request effectively does not demand a
regeneration event.
[0097] The SCR HC accumulation threshold corresponds with an SCR
catalyst performance threshold. Like described above, the
accumulation of HC on the SCR catalyst 50 may have a proportionally
negative effect on the performance of the SCR catalyst. For
example, the greater the accumulation of HC on the SCR catalyst 50,
the lower the conversion rate of NOx in the presence of ammonia or
the lower the NOx conversion efficiency. Accordingly, the SCR HC
accumulation threshold can be predetermined to correspond with a
minimum allowable performance characteristic, such as a minimum
allowable NOx conversion rate or efficiency. In this manner, the
SCR HC regeneration module 258 is configured to demand an SCR
catalyst regeneration event by generating the SCR HC regeneration
request 260 before the performance of the SCR catalyst 50 drops
below the minimum allowable performance characteristic. Because the
performance characteristics of the DOC 30 are different than those
of the SCR catalyst 50, the respective HC accumulation thresholds
can be different. For example, in certain implementations, the
performance of the DOC 30 may better tolerate HC accumulations than
the SCR catalyst 50. Accordingly, in such implementations, the HC
accumulation threshold of the DOC 30 may be higher than that of the
SCR catalyst 50. In AMOX other implementations, the HC accumulation
threshold of the DOC 30 may be lower than that of the SCR catalyst
50.
[0098] Before an SCR catalyst regeneration event according to the
SCR HC regeneration request 260 is initiated, the SCR HC
regeneration request is received by the HC regeneration arbitration
module 290, which determines whether the SCR HC regeneration
request has priority over other possible regeneration requests,
such as the DOC HC regeneration request 240 or other requests as
will be described in more detail below. If the HC regeneration
arbitration module 290 determines that the SCR HC regeneration
request 260 has priority, then the HC regeneration arbitration
module generates a HC regeneration command 122 that corresponds
with the regeneration event parameters demanded by the SCR HC
regeneration request.
[0099] The AMOX HC module 270 of the HC oxidation module 120 is
configured in a manner analogous to the DOC and SCR HC modules 230,
250 except the AMOX HC module applies to the AMOX catalyst 60
instead of the DOC 30 and SCR catalyst 50. For example, the AMOX HC
module 270 includes an AMOX HC storage module 272, AMOX HC release
module 274, AMOX HC accumulation module 276, and AMOX HC
regeneration module 278. The AMOX HC storage module 272 is
configured to estimate the amount of HC being stored on the AMOX
catalyst 60. According to the illustrated embodiment, the AMOX HC
storage module 272 estimates the amount or quantity of HC being
stored on the AMOX based on various inputs, such as, for example,
the SCR outlet HC 262 estimated by the SCR HC release module 254
(i.e., the quantity of HC in the exhaust gas exiting the SCR
catalyst 50 and entering the AMOX catalyst 60), the temperature of
the AMOX catalyst 60, and the mass flow rate of exhaust gas into
the AMOX catalyst. The temperature of the AMOX catalyst 60 (e.g.,
the catalyst bed of the AMOX catalyst) can be determined by the
AMOX HC storage module 272 according to any of various techniques,
such as using estimation modules and/or physical sensors. For
example, the temperature of the AMOX catalyst 60 can be determined
based on the difference between exhaust gas temperature
measurements taken by the temperature sensors 12 upstream and
downstream of the AMOX catalyst 60. Additionally, or alternatively,
the exhaust aftertreatment system 22 may have an AMOX catalyst
mid-bed temperature sensor that more directly detects the
temperature of the AMOX catalyst 60.
[0100] According to one embodiment, the quantity of HC being stored
on the AMOX catalyst 60, which can be expressed as the rate of HC
being stored on the AMOX catalyst, for a given SCR outlet HC value
262, can be obtained from a look-up table that is stored on the
AMOX HC storage module 272 and includes predetermined HC storage
rates on the AMOX catalyst 60 compared to AMOX catalyst temperature
values and exhaust mass flow rate values. The AMOX HC storage
module 272 can include a plurality of look-up tables each
associated with a given SCR outlet HC value 262. Accordingly, once
the temperature of the AMOX catalyst 60 and exhaust mass flow rate
is determined or known, the HC storage rate on the AMOX catalyst
estimated by the AMOX HC storage module 272 is the predetermined
value in the look-up table (associated with the determined SCR
outlet HC value 262) for the determined AMOX catalyst temperature
and exhaust flow rate values. For SCR outlet HC values 262 between
or outside those corresponding with the look-up tables,
interpolation or extrapolation techniques can be utilized to
estimate the AMOX HC storage rate.
[0101] The quantity of HC stored on the AMOX catalyst 60 over a
desired time period, which can be represented by the time input
192, is then estimated by the AMOX HC storage module 272 by
multiplying the estimated AMOX HC storage rate by the desired time
period. In certain implementations, the quantity of HC stored on
the AMOX catalyst 60 over the desired time period represents an
estimate of the newly stored HC on the AMOX catalyst, which can be
added to a previous estimate of the accumulation of HC on the AMOX
catalyst, as will be explained in more detail below, to obtain a
more accurate estimate of the quantity of HC currently stored on
the AMOX catalyst.
[0102] The AMOX HC release module 274 of the AMOX HC module 270 is
configured to estimate the AMOX outlet HC 282 (i.e., the amount or
quantity of HC being released from the AMOX catalyst 60) based on
various inputs, such as, for example, the temperature of the AMOX
catalyst and the quantity of HC stored on the AMOX catalyst. The
AMOX HC release module 274 may estimate the temperature of the AMOX
catalyst 60 in the same or similar manner as the AMOX HC storage
module 272, or simply utilize the temperature of the AMOX catalyst
estimated by the AMOX HC storage module. Similarly, the quantity of
HC stored on the AMOX catalyst 60 can be obtained from the AMOX HC
storage module 272 or can be based on a previous estimate of the
accumulation of HC on the AMOX catalyst 60.
[0103] According to one embodiment, the AMOX outlet HC 282 or
amount of HC being released from the AMOX catalyst 60, which can be
expressed as the rate of HC being released from the AMOX catalyst,
can be obtained from a look-up table that is stored on the AMOX HC
release module 274 and includes predetermined HC release rates from
the AMOX catalyst 60 compared to AMOX catalyst temperature values
and AMOX catalyst HC storage values. The AMOX HC release module 274
can include a plurality of look-up tables each associated with a
given AMOX outlet HC value 282. Accordingly, once the temperature
of the AMOX catalyst 60 and AMOX outlet HC value 282 is determined
or known, the HC release rate from the AMOX catalyst 60 estimated
by the AMOX HC release module 274 is the predetermined value in the
look-up table for the determined AMOX temperature and AMOX HC
storage values. The quantity of HC released from the AMOX catalyst
60 over a desired time period (e.g., the same desired time period
used by the AMOX HC storage module 272 to estimate the AMOX HC
storage), which also can be represented by the time input 192, is
then estimated by the AMOX HC release module 274 by multiplying the
estimated AMOX HC release rate by the desired time period.
[0104] The quantity of HC stored on the AMOX catalyst 60 estimated
by the AMOX HC storage module 272 and the AMOX outlet HC 282 (or
quantity of HC released from the AMOX catalyst) estimated by the
AMOX HC release module 274 is used by the AMOX HC accumulation
module 276 to estimate a total accumulation of HC on the AMOX
catalyst 60. The AMOX HC accumulation module 276 estimates the
total accumulation of HC on the AMOX catalyst 60 based on a
difference between the estimated quantity of HC stored on the AMOX
catalyst 60 and the estimated quantity of HC released from the AMOX
catalyst. In one implementation, the AMOX HC accumulation module
276 sets the total accumulation of HC on the AMOX catalyst 60 equal
to the difference between the estimated quantity of HC stored on
the AMOX catalyst and the estimated quantity of HC released from
the AMOX catalyst.
[0105] The AMOX HC regeneration module 278 generates an AMOX HC
regeneration request 280 based on a comparison between the total
accumulation of HC on the AMOX catalyst 60 estimated by the AMOX HC
accumulation module 276 and an AMOX HC accumulation threshold. In
one embodiment, the AMOX HC regeneration module 278 generates an
AMOX HC regeneration request 280 only when the total accumulation
of HC on the AMOX catalyst 60 estimated by the AMOX HC accumulation
module 276 meets (e.g., is equal to or exceeds) the AMOX HC
accumulation threshold. In such an embodiment, should the total
accumulation of HC on the AMOX catalyst 60 estimated by the AMOX HC
accumulation module 276 not meet the AMOX HC accumulation
threshold, then an AMOX HC regeneration request 280 is not
generated. The AMOX HC regeneration request 280 represents a demand
to regenerate the AMOX catalyst 60 at specific regeneration event
operating parameters (e.g., exhaust temperature, exhaust mass flow
rate, and timing parameter). The operating parameters of the AMOX
catalyst regeneration event demanded by the AMOX HC regeneration
request 280 may vary based on any of various factors, such as, for
example, the total accumulation of HC on the AMOX catalyst 60, the
period of time since the last AMOX catalyst regeneration event, and
the like. In some implementations, the HC regeneration request 280
is generated even if the total accumulation of HC on the AMOX
catalyst 60 does not meet the AMOX HC accumulation threshold.
However, in such implementations, the request 280 may be void of
regeneration event parameters, such that the request effectively
does not demand a regeneration event.
[0106] The AMOX HC accumulation threshold corresponds with an AMOX
catalyst performance threshold. Like described above, the
accumulation of HC on the AMOX catalyst 60 may have a
proportionally negative effect on the performance of the AMOX
catalyst. For example, the greater the accumulation of HC on the
AMOX catalyst 60, the lower the conversion rate of ammonia or the
lower the ammonia conversion efficiency. Accordingly, the AMOX HC
accumulation threshold can be predetermined to correspond with a
minimum allowable performance characteristic, such as a minimum
allowable ammonia conversion rate or efficiency. In this manner,
the AMOX HC regeneration module 278 is configured to demand an AMOX
catalyst regeneration event by generating the SCR HC regeneration
request 260 before the performance of the AMOX catalyst 60 drops
below the minimum allowable performance characteristic. Because the
performance characteristics of the DOC 30 and SCR catalyst 50 are
different than those of the AMOX catalyst 60, the respective HC
accumulation thresholds can be different. For example, in certain
implementations, the performance of the DOC 30 and/or SCR catalyst
50 may better tolerate HC accumulations than the AMOX catalyst 60.
Accordingly, in such implementations, the HC accumulation
thresholds of the DOC 30 and/or SCR catalyst 50 may be higher than
that of the AMOX catalyst 60. In other implementations, the HC
accumulation threshold of the DOC 30 and/or SCR catalyst 50 may be
lower than that of the AMOX catalyst 60.
[0107] According to certain embodiments, the AMOX HC regeneration
module 278 may include an exothermal module 280 that is configured
to monitor the exothermal conditions of the AMOX catalyst 60, which
include the heat generation of the AMOX catalyst. The AMOX HC
regeneration module 278 compares the exothermal conditions of the
AMOX catalyst 60 against predetermined thresholds and generates an
AMOX HC regeneration request 280 when the exothermal conditions
meet the associated thresholds. In one embodiment, an exothermal
condition is a heat generation rate of the AMOX catalyst 60, and an
exothermal condition threshold is a maximum heat generation rate of
the AMOX catalyst. The maximum heat generation rate of the AMOX
catalyst 60 may be associated with a rate above which an
uncontrolled or runaway regeneration of the AMOX catalyst may
occur. Alternatively, the exothermal condition is an amount of heat
generated by the AMOX catalyst 60, and the exothermal condition
threshold is a maximum allowable amount of heat generated by the
AMOX catalyst. The maximum allowable amount of heat generated by
the DOC 30 may be associated with a heat generation value above
which an uncontrolled or runaway regeneration of the DOC may occur.
Uncontrolled or runaway regenerations can be mitigated by
performing a controlled regeneration of the AMOX catalyst 60.
Accordingly, the AMOX HC regeneration module 278 is configured to
generate an AMOX HC regeneration request 280 demanding a
regeneration event when the exothermal condition meets the
exothermal condition threshold, or before an uncontrolled or
runaway regeneration event occurs. The parameters of the
regeneration event demanded by an AMOX HC regeneration request 280
generated from an exothermal condition threshold being met may be
different than an AMOX HC regeneration request generated from an
estimated total HC accumulation on the AMOX catalyst meeting an
AMOX HC accumulation threshold.
[0108] Before an AMOX catalyst regeneration event according to the
AMOX HC regeneration request 280 is initiated, the AMOX HC
regeneration request is received by the HC regeneration arbitration
module 290, which determines whether the AMOX HC regeneration
request has priority over other possible regeneration requests,
such as the DOC HC regeneration request 240, SCR HC regeneration
request 260, or other requests as will be described in more detail
below. If the HC regeneration arbitration module 290 determines
that the AMOX HC regeneration request 280 has priority, then the HC
regeneration arbitration module generates a HC regeneration command
122 that corresponds with the regeneration event parameters
demanded by the AMOX HC regeneration request.
[0109] The HC regeneration arbitration module 290 may include a
time-based regeneration module or algorithm configured to request a
regeneration event of the exhaust aftertreatment system 22 based on
the passing of a preset period of time since the last regeneration
event, which may be associated with a predetermined amount of fuel
consumed by the engine 20. Accordingly, the HC regeneration module
290 monitors the initiation and completion of regeneration events
of the exhaust aftertreatment system 22, and monitors the amount of
time since the completion of the latest regeneration event. The
time since the latent regeneration event can be determined from the
time input 292, which can be tied to an internal timer device of
the controller 100 or external timer device in communication with
the controller. When the preset time has been reached, the
time-based regeneration module of the HC regeneration arbitration
module 290 generates a time-based HC regeneration request that
demands a regeneration of the exhaust aftertreatment system 22 at
specific regeneration event operating parameters (e.g., exhaust
temperature, exhaust mass flow rate, and timing parameter). The HC
regeneration arbitration module 290 determines whether the
time-based HC regeneration request has priority over other possible
regeneration requests. If the HC regeneration arbitration module
290 determines that the time-based HC regeneration request has
priority, then the HC regeneration arbitration module generates a
HC regeneration command 122 that corresponds with the regeneration
event parameters demanded by the time-based HC regeneration
request.
[0110] The HC regeneration arbitration module 290 may include any
of various arbitration schemes for determining which of a plurality
of regeneration requests has priority. Such arbitration schemes may
take into account precalibrated regeneration timers, system
efficiency monitors, and accumulation thresholds that are set based
on the impact of HC on the performance and emissions behavior of
one or more of the aftertreatment components of the system 22. For
example, the winning request could represent the component that is
most severely impacted by HC effects if the precalibrated timer has
not timed-out and the system efficiency is still normal.
[0111] The regeneration event parameters demanded by the DOC, SCR,
AMOX, and time-based HC regeneration requests can be different. For
example, one request may demand a shorter regeneration event that
is sufficient to clean HC from a corresponding component, but
insufficient to clean HC from another component. Or, as another
example, one request may demand a regeneration event with a lower
exhaust gas temperature that is sufficient to clean HC from a
corresponding component, but insufficient to clean HC from another
component. To account for such discrepancies, the HC modules 230,
250, 270 of the HC oxidation module 120 continue to operate as
described above during a regeneration event to continuously monitor
the storage, release, and accumulation of HC on the components
while regeneration events are occurring, even if the regeneration
event was triggered for a single component. For example, the extra
HC being released from the DOC 30 during a regeneration event is
accounted for in the calculation of the DOC outlet HC 242 as extra
HC being introduced into the SCR catalyst 50. In this manner, an
accurate and current estimate of the HC accumulation status for
each component is known before, during, and after any regeneration
event.
[0112] In certain embodiments of a controller 100 having both a
sulfur oxidation module 110 and hydrocarbon oxidation module 120,
the sulfur and HC regeneration arbitration modules 190, 290 may be
combined to form a single arbitration module. The single
arbitration module would be configured to arbitrate between sulfur
regeneration requests and HC regeneration requests to determine
which of multiple requests has priority.
[0113] Although not shown, the controller 100 can include other
poison oxidation modules configured analogously to the sulfur and
HC oxidation modules 110, 120 to estimate poison accumulation
levels on the components of the exhaust aftertreatment system 22
and request regeneration events if the poison accumulation levels
reach corresponding predetermined thresholds. For example, the
controller 100 can include a water oxidation module that estimate
water accumulation levels on the components of the exhaust
aftertreatment system 22 and requests regenerations event if the
water accumulation levels reach corresponding predetermined water
accumulation thresholds. Other poisons can include platinum (or
other precious metals migrated from the DOC 30 to the SCR catalyst
50, alkali salts (e.g., Na and K from contaminated urea solutions),
and phosphorus and zinc from lubrication oil. Additionally, the
thermal degradation of a catalyst, which is characterized by the
progressive loss of reaction sites, can be considered a type of
poison applicable to the present disclosure.
[0114] Additionally, although not shown, for embodiments with
exhaust aftertreatment systems 22 that include a DPF 40, each of
the sulfur and hydrocarbon oxidation modules 110, 120 of the
controller 100 can include a DPF sulfur and HC module,
respectively. In such embodiments, the DPF sulfur and HC modules
are configured in a manner analogous to the DOC, SCR, and AMOX
sulfur modules 130, 150, 170, and the SCR HC module 250,
respectively, except the DPF sulfur and HC modules apply to the
condition and regeneration of the DPF 40.
[0115] Referring to FIG. 5, a method 300 for separately estimating
conditions of aftertreatment system components and regenerating the
components is shown. In certain implementations, the steps of the
method 300 may be executed by the modules of the controller 100
described above.
[0116] The method 300 begins by estimating the quantity of a poison
accumulated on a DOC at 310. If the poison accumulation on the DOC
is above or at least meets an associated threshold at 320, then the
method 300 commands a regeneration of the DOC at 380, which at
least partially regenerates other components of the aftertreatment
system. However, if the poison accumulation on the DOC is below or
does not meet the associated threshold at 320, then the method 300
proceeds to estimate the quantity of a poison accumulated on an SCR
catalyst at 330. If the poison accumulation on the SCR catalyst is
above or at least meets an associated threshold at 340, then the
method 300 commands a regeneration of the SCR catalyst at 380,
which at least partially regenerates other components of the
aftertreatment system. However, if the poison accumulation on the
SCR catalyst is below or does not meet the associated threshold at
340, then the method 300 proceeds to estimate the quantity of a
poison accumulated on an AMOX catalyst at 350. If the poison
accumulation on the AMOX catalyst is above or at least meets an
associated threshold at 360, then the method 300 commands a
regeneration of the AMOX catalyst at 380, which at least partially
regenerates other components of the aftertreatment system. However,
if the poison accumulation on the AMOX catalyst is below or does
not meet the associated threshold at 360, then the method 300
proceeds to determine if a predetermined period of time has passed
since a previous regeneration event at 370. If the predetermined
period of time has passed at 370, then the method 300 commands a
regeneration of the components of the aftertreatment system.
However, if the predetermined period of time has not passed at 370,
then the method 300 does not command a regeneration event and
ends.
[0117] In certain implementations, the poison of the method 300 can
be one or both of sulfur and HC. In some implementations, the
poison of the method 300 can be water. According to some
embodiments, the estimation of the accumulation of the poison on
the SCR catalyst at 330 is at least indirectly dependent on the
estimate of the accumulation of the poison on the DOC Likewise, the
estimation of the accumulation of the poison on the AMOX catalyst
at 370 can be at least indirectly dependent on the estimate of the
accumulation of the poison on the SCR catalyst. Also, in some
embodiments, the estimation of the poison accumulation on the DOC,
SCR catalyst, and AMOX catalyst includes estimations of the amount
of poison being stored and the amount of poison being released from
the DOC, SCR catalyst, and AMOX catalyst, respectively. Although
not shown, in some implementations, the method 300 may include
estimating an exothermic condition for each of the DOC and AMOX
catalysts, and command a regeneration event at 380 if the
exothermic condition for the DOC and AMOX catalysts meet an
associated threshold.
[0118] The schematic flow chart diagrams and method schematic
diagrams described above are generally set forth as logical flow
chart diagrams. As such, the depicted order and labeled steps are
indicative of representative embodiments. Other steps, orderings
and methods may be conceived that are equivalent in function,
logic, or effect to one or more steps, or portions thereof, of the
methods illustrated in the schematic diagrams.
[0119] Additionally, the format and symbols employed are provided
to explain the logical steps of the schematic diagrams and are
understood not to limit the scope of the methods illustrated by the
diagrams. Although various arrow types and line types may be
employed in the schematic diagrams, they are understood not to
limit the scope of the corresponding methods. Indeed, some arrows
or other connectors may be used to indicate only the logical flow
of a method. For instance, an arrow may indicate a waiting or
monitoring period of unspecified duration between enumerated steps
of a depicted method. Additionally, the order in which a particular
method occurs may or may not strictly adhere to the order of the
corresponding steps shown. It will also be noted that each block of
the block diagrams and/or flowchart diagrams, and combinations of
blocks in the block diagrams and/or flowchart diagrams, can be
implemented by special purpose hardware-based systems that perform
the specified functions or acts, or combinations of special purpose
hardware and program code.
[0120] Many of the functional units described in this specification
have been labeled as modules, in order to more particularly
emphasize their implementation independence. For example, a module
may be implemented as a hardware circuit comprising custom VLSI
circuits or gate arrays, off-the-shelf semiconductors such as logic
chips, transistors, or other discrete components. A module may also
be implemented in programmable hardware devices such as field
programmable gate arrays, programmable array logic, programmable
logic devices or the like.
[0121] Modules may also be implemented in software for execution by
various types of processors. An identified module of executable
code may, for instance, comprise one or more physical or logical
blocks of computer instructions, which may, for instance, be
organized as an object, procedure, or function. Nevertheless, the
executables of an identified module need not be physically located
together, but may comprise disparate instructions stored in
different locations which, when joined logically together, comprise
the module and achieve the stated purpose for the module.
[0122] Indeed, a module of computer readable program code may be a
single instruction, or many instructions, and may even be
distributed over several different code segments, among different
programs, and across several memory devices. Similarly, operational
data may be identified and illustrated herein within modules, and
may be embodied in any suitable form and organized within any
suitable type of data structure. The operational data may be
collected as a single data set, or may be distributed over
different locations including over different storage devices, and
may exist, at least partially, merely as electronic signals on a
system or network. Where a module or portions of a module are
implemented in software, the computer readable program code may be
stored and/or propagated on in one or more computer readable
medium(s).
[0123] The computer readable medium may be a tangible computer
readable storage medium storing the computer readable program code.
The computer readable storage medium may be, for example, but not
limited to, an electronic, magnetic, optical, electromagnetic,
infrared, holographic, micromechanical, or semiconductor system,
apparatus, or device, or any suitable combination of the
foregoing.
[0124] More specific examples of the computer readable medium may
include but are not limited to a portable computer diskette, a hard
disk, a random access memory (RAM), a read-only memory (ROM), an
erasable programmable read-only memory (EPROM or Flash memory), a
portable compact disc read-only memory (CD-ROM), a digital
versatile disc (DVD), an optical storage device, a magnetic storage
device, a holographic storage medium, a micromechanical storage
device, or any suitable combination of the foregoing. In the
context of this document, a computer readable storage medium may be
any tangible medium that can contain, and/or store computer
readable program code for use by and/or in connection with an
instruction execution system, apparatus, or device.
[0125] The computer readable medium may also be a computer readable
signal medium. A computer readable signal medium may include a
propagated data signal with computer readable program code embodied
therein, for example, in baseband or as part of a carrier wave.
Such a propagated signal may take any of a variety of forms,
including, but not limited to, electrical, electro-magnetic,
magnetic, optical, or any suitable combination thereof. A computer
readable signal medium may be any computer readable medium that is
not a computer readable storage medium and that can communicate,
propagate, or transport computer readable program code for use by
or in connection with an instruction execution system, apparatus,
or device. Computer readable program code embodied on a computer
readable signal medium may be transmitted using any appropriate
medium, including but not limited to wireless, wireline, optical
fiber cable, Radio Frequency (RF), or the like, or any suitable
combination of the foregoing
[0126] In one embodiment, the computer readable medium may comprise
a combination of one or more computer readable storage mediums and
one or more computer readable signal mediums. For example, computer
readable program code may be both propagated as an electro-magnetic
signal through a fiber optic cable for execution by a processor and
stored on RAM storage device for execution by the processor.
[0127] Computer readable program code for carrying out operations
for aspects of the present invention may be written in any
combination of one or more programming languages, including an
object oriented programming language such as Java, Smalltalk, C++
or the like and conventional procedural programming languages, such
as the "C" programming language or similar programming languages.
The computer readable program code may execute entirely on the
user's computer, partly on the user's computer, as a stand-alone
software package, partly on the user's computer and partly on a
remote computer or entirely on the remote computer or server. In
the latter scenario, the remote computer may be connected to the
user's computer through any type of network, including a local area
network (LAN) or a wide area network (WAN), or the connection may
be made to an external computer (for example, through the Internet
using an Internet Service Provider).
[0128] The program code may also be stored in a computer readable
medium that can direct a computer, other programmable data
processing apparatus, or other devices to function in a particular
manner, such that the instructions stored in the computer readable
medium produce an article of manufacture including instructions
which implement the function/act specified in the schematic
flowchart diagrams and/or schematic block diagrams block or
blocks.
[0129] The program code may also be loaded onto a computer, other
programmable data processing apparatus, or other devices to cause a
series of operational steps to be performed on the computer, other
programmable apparatus or other devices to produce a computer
implemented process such that the program code which executed on
the computer or other programmable apparatus provide processes for
implementing the functions/acts specified in the flowchart and/or
block diagram block or blocks.
[0130] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
present invention. Thus, appearances of the phrases "in one
embodiment," "in an embodiment," and similar language throughout
this specification may, but do not necessarily, all refer to the
same embodiment. Similarly, the use of the term "implementation"
means an implementation having a particular feature, structure, or
characteristic described in connection with one or more embodiments
of the present disclosure, however, absent an express correlation
to indicate otherwise, an implementation may be associated with one
or more embodiments.
[0131] The present disclosure may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the disclosure is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *