U.S. patent application number 15/137393 was filed with the patent office on 2017-10-26 for catalyst failure detection based combined ammonia to nox ratios, conversion inefficiency values and ammonia slip values.
This patent application is currently assigned to Cummins Emission Solutions Inc.. The applicant listed for this patent is Cummins Emission Solutions Inc.. Invention is credited to Michael Haas, An Wu.
Application Number | 20170306827 15/137393 |
Document ID | / |
Family ID | 60022359 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306827 |
Kind Code |
A1 |
Wu; An ; et al. |
October 26, 2017 |
Catalyst Failure Detection Based Combined Ammonia to NOx Ratios,
Conversion Inefficiency Values and Ammonia Slip Values
Abstract
Implementations of systems and methods for detecting the failure
of an selective catalytic reduction (SCR) catalyst may include a
controller or one or more circuits for acquiring an ammonia to NOx
ratio (ANR) value for exhaust gas flowing through an exhaust
system, acquiring a conversion inefficiency value indicative of a
conversion inefficiency of the SCR catalyst, acquire an NH.sub.3
slip value indicative of an amount of NH.sub.3 slip through the
exhaust system downstream of the SCR catalyst, calculate a combined
ANR/conversion inefficiency/NH3 slip (ACN) value based on the ANR
value, conversion inefficiency value, and NH.sub.3 slip value, and
indicating a failure of the SCR catalyst responsive to the
calculated ACN value exceeding a predetermined threshold value.
Inventors: |
Wu; An; (Columbus, IN)
; Haas; Michael; (Columbus, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cummins Emission Solutions Inc. |
Columbus |
IN |
US |
|
|
Assignee: |
Cummins Emission Solutions
Inc.
Columbus
IN
|
Family ID: |
60022359 |
Appl. No.: |
15/137393 |
Filed: |
April 25, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/47 20130101;
F01N 3/208 20130101; Y02T 10/24 20130101; Y02T 10/12 20130101; Y02A
50/2325 20180101; F01N 11/007 20130101; F01N 2550/02 20130101; Y02T
10/40 20130101; Y02A 50/20 20180101 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 3/20 20060101 F01N003/20 |
Claims
1. A system comprising: an exhaust system including a selective
catalytic reduction (SCR) catalyst; and a controller configured to:
acquire an ammonia to NOx ratio (ANR) value for exhaust gas flowing
through the exhaust system; acquire a conversion inefficiency value
indicative of a conversion inefficiency of the SCR catalyst;
acquire an NH.sub.3 slip value indicative of an amount of NH.sub.3
slip through the exhaust system downstream of the SCR catalyst;
calculate a combined ANR/conversion inefficiency/NH3 slip (ACN)
value based on the acquired ANR value, the acquired conversion
inefficiency value, and the acquired NH.sub.3 slip value; and
indicate a failure of the SCR catalyst responsive to the calculated
ACN value exceeding a predetermined threshold value.
2. The system of claim 1 further comprising an NH.sub.3 sensor
positioned relative to the exhaust system to detect an amount of
NH.sub.3 slip downstream of at least a portion of the SCR catalyst,
wherein acquiring the NH.sub.3 slip value is based on the detected
amount of NH.sub.3 slip by the NH.sub.3 sensor.
3. The system of claim 1, wherein acquiring the ANR value includes
acquiring a filtered value of an ANR parameter determined based on
a feedback control algorithm of the controller.
4. The system of claim 1, further comprising a NH.sub.3 sensor
positioned relative to the exhaust system, wherein acquiring the
ANR value is based on a detected amount of NH.sub.3 by the NH.sub.3
sensor.
5. The system of claim 1, further comprising a NO.sub.x sensor
positioned relative to the exhaust system, wherein acquiring the
ANR value is based on a detected amount of NO.sub.x by the NO.sub.x
sensor.
6. The system of claim 1, wherein acquiring the conversion
inefficiency value includes acquiring an actual conversion
efficiency value for the SCR catalyst and an estimated target
conversion efficiency value for the SCR catalyst.
7. The system of claim 6, wherein the conversion inefficiency value
is calculated by: C = ( 1 - CE CE Target ) .times. 100
##EQU00004##
8. The system of claim 6, wherein the actual conversion efficiency
value is an estimated value.
9. The system of claim 6, wherein the actual conversion efficiency
value is based on a measured value of NO.sub.x by a NO.sub.x sensor
upstream of the SCR catalyst and a NO.sub.x sensor downstream of at
least a portion of the SCR catalyst.
10. The system of claim 1, wherein the predetermined threshold
value is a value based on empirical data where 95% of SCR catalysts
have failed above the threshold value.
11. The system of claim 1, wherein indicating the failure of the
SCR catalyst comprises lighting a malfunction indicator lamp.
12. The system of claim 1, wherein indicating the failure of the
SCR catalyst comprises setting a value for a parameter to a value
indicating that the SCR catalyst has failed.
13. A controller comprising: an ammonia to NOx ratio (ANR) circuit
configured to determine an ANR value for an exhaust system
including a selective catalytic reduction (SCR) catalyst; a
deNO.sub.x conversion inefficiency circuit configured to calculate
a conversion inefficiency value based on an actual conversion
efficiency for the SCR catalyst and an estimated target conversion
efficiency for the SCR catalyst; a NH.sub.3 slip circuit configured
to determine an NH.sub.3 slip value for the exhaust system; and a
combined ANR/conversion inefficiency/NH3 slip (ACN) circuit
configured to: receive the NH.sub.3 slip value from the NH.sub.3
slip circuit, the ANR value from the ANR circuit, and the
conversion inefficiency value from the deNO.sub.x conversion
inefficiency circuit, determine an ACN value based on the NH.sub.3
slip value, the ANR value, and the conversion inefficiency value,
compare the determined ACN value to a predetermined threshold
value, and indicate a failure of the SCR catalyst responsive to the
determined ACN value exceeding a predetermined threshold value.
14. The controller of claim 13, wherein the NH.sub.3 slip value is
based on a detected amount of NH.sub.3 slip by a NH.sub.3
sensor.
15. The controller of claim 13, wherein the ANR value is a filtered
value of an ANR parameter determined based on a feedback control
algorithm.
16. The controller of claim 13, wherein the ANR value is based on a
detected amount of NH.sub.3 by the NH.sub.3 sensor or a detected
amount of NO.sub.x by the NO.sub.x sensor.
17. The controller of claim 13, wherein the actual conversion
efficiency value is an estimated value.
18. The controller of claim 13, wherein the actual conversion
efficiency value is based on a measured value of NO.sub.x by a
NO.sub.x sensor upstream of the SCR catalyst and a NO.sub.x sensor
downstream of at least a portion of the SCR catalyst.
19. The controller of claim 13, wherein indicating the failure of
the SCR catalyst comprises lighting a malfunction indicator
lamp.
20. The controller of claim 13, wherein indicating the failure of
the SCR catalyst comprises setting a value for a parameter to a
value indicating that the SCR catalyst has failed.
21. A method for indicating a failure of a selective catalytic
reduction (SCR) catalyst of an exhaust system, the method
comprising: acquiring an ammonia to NOx ratio (ANR) value for
exhaust gas flowing through the exhaust system; acquiring a
conversion inefficiency value indicative of a conversion
inefficiency of the SCR catalyst; acquiring an NH.sub.3 slip value
indicative of an amount of NH.sub.3 slip through the exhaust system
downstream of the SCR catalyst; calculating a combined
ANR/conversion inefficiency/NH3 slip (ACN) value based on the
acquired ANR value, the acquired conversion inefficiency value, and
the acquired NH.sub.3 slip value; and indicating a failure of the
SCR catalyst responsive to the calculated ACN value exceeding a
predetermined threshold value.
22. The method of claim 21, wherein the NH.sub.3 slip value is
based on a detected amount of NH.sub.3 slip by a NH.sub.3
sensor.
23. The method of claim 21, wherein the ANR value is based on a
detected amount of NH.sub.3 by the NH.sub.3 sensor or a detected
amount of NO.sub.x by the NO.sub.x sensor.
24. The method of claim 21, wherein the conversion inefficiency
value is based on an actual conversion efficiency value and an
estimated target conversion efficiency value, wherein the actual
conversion efficiency value is based on a measured value of
NO.sub.x by a NO.sub.x sensor upstream of the SCR catalyst and a
NO.sub.x sensor downstream of at least a portion of the SCR
catalyst.
25. The method of claim 21, wherein indicating the failure of the
SCR catalyst comprises lighting a malfunction indicator lamp or
setting a value for a parameter to a value indicating that the SCR
catalyst has failed.
Description
TECHNICAL FIELD
[0001] The present application relates generally to the field of
aftertreatment systems for internal combustion engines.
BACKGROUND
[0002] For internal combustion engines, such as diesel engines,
nitrogen oxide (NO.sub.x) compounds may be emitted in the exhaust.
To reduce NO.sub.x emissions, a selective catalytic reduction (SCR)
process may be implemented to convert the NO.sub.x compounds into
more neutral compounds, such as diatomic nitrogen, water, or carbon
dioxide, with the aid of a catalyst and a reductant. The catalyst
may be included in a catalyst chamber of an exhaust system, such as
that of a vehicle or power generation unit. A reductant, such as
anhydrous ammonia, aqueous ammonia, or urea, is typically
introduced into the exhaust gas flow prior to the catalyst chamber.
To introduce the reductant into the exhaust gas flow for the SCR
process, an SCR system may dose or otherwise introduce the
reductant through a dosing module that vaporizes or sprays the
reductant into an exhaust pipe of the exhaust system up-stream of
the catalyst chamber. The SCR system may include one or more
sensors to monitor conditions within the exhaust system.
SUMMARY
[0003] Implementations described herein relate to systems and
methods for detecting the failure of an SCR catalyst. If an SCR
catalyst fails, then unwanted NO.sub.x emissions may be exhausted
to atmosphere due to the decrease or cessation of the selective
catalytic reduction process for the exhaust system. In some
implementations, to increase the robustness of the testing for the
failure of the SCR catalyst and/or to reduce potential
false-positives for failed SCR catalysts, multiple parameters or
signatures may be used to generate a composite value. For instance,
the three parameters or signatures may include an ammonia to
NO.sub.x ratio (ANR), a deNO.sub.x conversion inefficiency, and a
NH.sub.3 slip indicator. Each value for the ANR, deNO.sub.x
conversion inefficiency, and NH.sub.3 slip indicator can be
multiplied together to form an aggregate value, such as a combined
ANR/conversion inefficiency/NH3 slip (ACN) value, that can be used
to indicate when the SCR catalyst has failed. When the ACN value
exceeds a predetermined threshold value, the SCR catalyst can be
determined to have likely failed. The use of the multiple
parameters or signatures for the ACN value decreases the likelihood
that a single outlier value for a parameter or signature will
trigger the indication that the SCR catalyst has failed.
[0004] One implementation relates to a system that includes exhaust
system having an SCR catalyst and a controller. The controller is
configured to acquire an ANR value for exhaust gas flowing through
the exhaust system, acquire a conversion inefficiency value
indicative of a conversion inefficiency of the SCR catalyst,
acquire an NH.sub.3 slip value indicative of an amount of NH.sub.3
slip through the exhaust system downstream of the SCR catalyst,
calculate an ACN value based on the acquired ANR value, the
acquired conversion inefficiency value, and the acquired NH.sub.3
slip value, and indicate a failure of the SCR catalyst responsive
to the calculated ACN value exceeding a predetermined threshold
value.
[0005] In some implementations, the system also includes an
NH.sub.3 sensor positioned relative to the exhaust system to detect
an amount of NH.sub.3 slip downstream of at least a portion of the
SCR catalyst and acquiring the NH.sub.3 slip value is based on the
detected amount of NH.sub.3 slip by the NH.sub.3 sensor. In some
implementations, acquiring the ANR value includes acquiring a
filtered value of an ANR parameter determined based on a feedback
control algorithm of the controller. In some implementations, the
system also includes a NH.sub.3 sensor positioned relative to the
exhaust system and acquiring the ANR value is based on a detected
amount of NH.sub.3 by the NH.sub.3 sensor. In some implementations,
the system also includes a NO.sub.x sensor positioned relative to
the exhaust system and acquiring the ANR value is based on a
detected amount of NO.sub.x by the NO.sub.x sensor. In some
implementations, acquiring the conversion inefficiency value
includes acquiring an actual conversion efficiency value for the
SCR catalyst and an estimated target conversion efficiency value
for the SCR catalyst. The conversion inefficiency value may be
calculated by:
C = ( 1 - CE CE Target ) .times. 100 ##EQU00001##
In some instances, the actual conversion efficiency value is an
estimated value or the actual conversion efficiency value may be
based on a measured value of NO.sub.x by a NO.sub.x sensor upstream
of the SCR catalyst and a NO.sub.x sensor downstream of at least a
portion of the SCR catalyst. In some implementations, the
predetermined threshold value is a value based on empirical data
where 95% of SCR catalysts have failed above the threshold value.
In some implementations, indicating the failure of the SCR catalyst
includes lighting a malfunction indicator lamp. In some
implementations, indicating the failure of the SCR catalyst
includes setting a value for a parameter to a value indicating that
the SCR catalyst has failed.
[0006] Another implementation relates to a controller that includes
an ANR circuit configured to determine an ANR value for an exhaust
system including an SCR catalyst, a deNO.sub.x conversion
inefficiency circuit configured to calculate a conversion
inefficiency value based on an actual conversion efficiency for the
SCR catalyst and an estimated target conversion efficiency for the
SCR catalyst, a NH.sub.3 slip circuit configured to determine an
NH.sub.3 slip value for the exhaust system, and an ACN circuit. The
ACN circuit is configured to receive the NH.sub.3 slip value from
the NH.sub.3 slip circuit, the ANR value from the ANR circuit, and
the conversion inefficiency value from the deNO.sub.x conversion
inefficiency circuit. The ACN circuit is also configured to
determine an ACN value based on the NH.sub.3 slip value, the ANR
value, and the conversion inefficiency value and compare the
determined ACN value to a predetermined threshold value. The ACN
circuit is further configured to indicate a failure of the SCR
catalyst responsive to the determined ACN value exceeding a
predetermined threshold value.
[0007] In some implementations, the NH.sub.3 slip value is based on
a detected amount of NH.sub.3 slip by a NH.sub.3 sensor. In some
implementations, the ANR value is a filtered value of an ANR
parameter determined based on a feedback control algorithm. In some
implementations, the ANR value is based on a detected amount of
NH.sub.3 by the NH.sub.3 sensor or a detected amount of NO.sub.x by
the NO.sub.x sensor. In some implementations, the actual conversion
efficiency value is an estimated value. In some implementations,
the actual conversion efficiency value is based on a measured value
of NO.sub.x by a NO.sub.x sensor upstream of the SCR catalyst and a
NO.sub.x sensor downstream of at least a portion of the SCR
catalyst. In some implementations, indicating the failure of the
SCR catalyst includes lighting a malfunction indicator lamp. In
some implementations, indicating the failure of the SCR catalyst
includes setting a value for a parameter to a value indicating that
the SCR catalyst has failed.
[0008] Yet a further implementation relates to a method for
indicating a failure of an SCR catalyst of an exhaust system. The
method includes acquiring an ANR value for exhaust gas flowing
through the exhaust system, acquiring a conversion inefficiency
value indicative of a conversion inefficiency of the SCR catalyst,
acquiring an NH.sub.3 slip value indicative of an amount of
NH.sub.3 slip through the exhaust system downstream of the SCR
catalyst, calculating an ACN value based on the acquired ANR value,
the acquired conversion inefficiency value, and the acquired
NH.sub.3 slip value, and indicating a failure of the SCR catalyst
responsive to the calculated ACN value exceeding a predetermined
threshold value.
[0009] In some implementations, the NH.sub.3 slip value is based on
a detected amount of NH.sub.3 slip by a NH.sub.3 sensor. In some
implementations, the ANR value is based on a detected amount of
NH.sub.3 by the NH.sub.3 sensor or a detected amount of NO.sub.x by
the NO.sub.x sensor. In some implementations, the conversion
inefficiency value is based on an actual conversion efficiency
value and an estimated target conversion efficiency value, where
the actual conversion efficiency value is based on a measured value
of NO.sub.x by a NO.sub.x sensor upstream of the SCR catalyst and a
NO.sub.x sensor downstream of at least a portion of the SCR
catalyst. In some implementations, indicating the failure of the
SCR catalyst comprises lighting a malfunction indicator lamp or
setting a value for a parameter to a value indicating that the SCR
catalyst has failed.
BRIEF DESCRIPTION
[0010] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other
features, aspects, and advantages of the disclosure will become
apparent from the description, the drawings, and the claims, in
which:
[0011] FIG. 1 is a block schematic diagram of an example selective
catalytic reduction system having an example reductant delivery
system for an exhaust system;
[0012] FIG. 2 is a graphical diagram of values for an NH.sub.3 slip
indicator, ANR, deNO.sub.x conversion inefficiency, and ACN for an
operational SCR catalyst and a failed SCR catalyst;
[0013] FIG. 3 is a block diagram of a controller having an SCR
failure detection circuit;
[0014] FIG. 4 is a flow diagram of a process to calculate an ACN
value based on the NH.sub.3 slip indicator, ANR, and deNO.sub.x
conversion inefficiency values;
[0015] FIG. 5 is a graphical diagram of values for an NH.sub.3 slip
indicator, screening delay flag, combined ANR and deNO.sub.x
conversion inefficiency, and ACN highlighting values before and
after a transport delay; and
[0016] FIG. 6 is a process diagram for determining and indicating
that an SCR catalyst has failed.
[0017] It will be recognized that some or all of the figures are
schematic representations for purposes of illustration. The figures
are provided for the purpose of illustrating one or more
implementations with the explicit understanding that they will not
be used to limit the scope or the meaning of the claims.
DETAILED DESCRIPTION
[0018] Following below are more detailed descriptions of various
concepts related to, and implementations of, methods, apparatuses,
and systems for detecting the failure of an SCR catalyst. The
various concepts introduced above and discussed in greater detail
below may be implemented in any of numerous ways, as the described
concepts are not limited to any particular manner of
implementation. Examples of specific implementations and
applications are provided primarily for illustrative purposes.
I. Overview
[0019] For applications that utilize diesel engines (e.g.,
vehicles, power generators, etc.), an SCR process may be employed
to reduce unwanted NO.sub.x compounds from the exhaust gas prior to
emission to atmosphere. The SCR process utilizes an SCR catalyst
with dosed reductant, such as ammonia, to reduce the NO.sub.x
compounds into neutral compounds, such as diatomic nitrogen, water,
or carbon dioxide. The SCR catalyst provides a carrier (e.g., a
ceramic material) and oxides or base metals, zeolites, and/or other
precious metals as active components to assist in the reduction of
the NO.sub.x compounds. If the SCR catalyst degrades, such as due
to aging, deactivation, etc., or otherwise fails, then increased
amounts of NO.sub.x compounds may be released in the emissions from
the system. Thus, detection of when an SCR catalyst fails may be
important to reduce the likelihood of NO.sub.x compounds being
emitted from the system. Moreover, while the use of a single signal
or signature may be used for detecting the failure of the catalyst,
such a single signal or signature may result in false-positives
indicating an SCR catalyst has failed when it is still viable. Such
false-positives may result from sensor failures and/or errors. In
addition, the false-positives may result in an SCR catalyst being
unnecessarily discarded and/or removed and tested while the
catalyst is still operable.
[0020] Accordingly, to increase the robustness of the testing for
the failure of the SCR catalyst and/or to reduce potential
false-positives for failed SCR catalysts, multiple parameters or
signatures may be used to generate a composite value indicative of
the operating status of the SCR catalyst. For instance, three
parameters or signatures may be used, including ANR, a deNO.sub.x
conversion inefficiency, and a NH.sub.3 slip indicator. Each value
for the ANR, deNO.sub.x conversion inefficiency, and NH.sub.3 slip
indicator can be multiplied together to form an aggregate value,
such as an ACN value, that can be used to indicate when the SCR
catalyst has failed. When the ACN value exceeds a predetermined
threshold value, the SCR catalyst can be determined to have likely
failed. The use of the multiple parameters or signatures for the
ACN value decreases the likelihood that an outlier value for a
parameter or signature will trigger the indication that the SCR
catalyst has failed.
II. Overview of Aftertreatment System
[0021] FIG. 1 depicts an aftertreatment system 100 having an
example reductant delivery system 110 for an exhaust system 190.
The aftertreatment system 100 includes a diesel particulate filter
(DPF) 102, the reductant delivery system 110, a decomposition
chamber or reactor 104, a SCR catalyst 106, and a sensor 150.
[0022] The DPF 102 is configured to remove particulate matter, such
as soot, from exhaust gas flowing in the exhaust system 190. The
DPF 102 includes an inlet, where the exhaust gas is received, and
an outlet, where the exhaust gas exits after having particulate
matter substantially filtered from the exhaust gas and/or
converting the particulate matter into carbon dioxide.
[0023] The decomposition chamber 104 is configured to convert a
reductant, such as urea, aqueous ammonia, or diesel exhaust fluid
(DEF), into ammonia. The decomposition chamber 104 includes a
reductant delivery system 110 having a dosing module 112 configured
to dose the reductant into the decomposition chamber 104. In some
implementations, the reductant is injected upstream of the SCR
catalyst 106. The reductant droplets then undergo the processes of
evaporation, thermolysis, and hydrolysis to form gaseous ammonia
within the exhaust system 190. The decomposition chamber 104
includes an inlet in fluid communication with the DPF 102 to
receive the exhaust gas containing NO.sub.x emissions and an outlet
for the exhaust gas, NO.sub.x emissions, ammonia, and/or remaining
reductant to flow to the SCR catalyst 106.
[0024] The decomposition chamber 104 includes the dosing module 112
mounted to the decomposition chamber 104 such that the dosing
module 112 may dose the reductant into the exhaust gases flowing in
the exhaust system 190. The dosing module 112 may include an
insulator 114 interposed between a portion of the dosing module 112
and the portion of the decomposition chamber 104 to which the
dosing module 112 is mounted. The dosing module 112 is fluidly
coupled to one or more reductant sources 116. In some
implementations, a pump 118 may be used to pressurize the reductant
from the reductant source 116 for delivery to the dosing module
112.
[0025] The dosing module 112 and pump 118 are also electrically or
communicatively coupled to a controller 120. The controller 120 is
configured to control the dosing module 112 to dose reductant into
the decomposition chamber 104. The controller 120 may also be
configured to control the pump 118. The controller 120 may also be
electrically coupled to a warning lamp, such as a malfunction
indicator lamp (MIL), and/or communicatively coupled to a storage
device to modify a value of one or more parameters stored in the
storage device.
[0026] The controller 120 may include a microprocessor, an
application-specific integrated circuit (ASIC), a
field-programmable gate array (FPGA), etc., or combinations
thereof. The controller 120 may include memory which may include,
but is not limited to, electronic, optical, magnetic, or any other
storage or transmission device capable of providing a processor,
ASIC, FPGA, etc. with program instructions. The memory may include
a memory chip, Electrically Erasable Programmable Read-Only Memory
(EEPROM), erasable programmable read only memory (EPROM), flash
memory, or any other suitable memory from which the controller 120
can read instructions. The instructions may include code from any
suitable programming language.
[0027] The SCR catalyst 106 is configured to assist in the
reduction of NO.sub.x emissions by accelerating a NO.sub.x
reduction process between the ammonia and the NO.sub.x of the
exhaust gas into diatomic nitrogen, water, and/or carbon dioxide.
The SCR catalyst 106 includes inlet in fluid communication with the
decomposition chamber 104 from which exhaust gas and reductant is
received and an outlet in fluid communication with an end of the
exhaust system 190.
[0028] The exhaust system 190 may further include a diesel
oxidation catalyst (DOC) in fluid communication with the exhaust
system 190 (e.g., downstream of the SCR catalyst 106 or upstream of
the DPF 102) to oxidize hydrocarbons and carbon monoxide in the
exhaust gas.
[0029] In some implementations, the DPF 102 may be positioned
downstream of the decomposition chamber or reactor pipe 104. For
instance, the DPF 102 and the SCR catalyst 106 may be combined into
a single unit, such as an SDPF. In some implementations, the dosing
module 112 may instead be positioned downstream of a turbocharger
or upstream of a turbocharger.
[0030] The sensor 150 may be coupled to the exhaust system 190 to
detect a condition of the exhaust gas flowing through the exhaust
system 190. In some implementations, the sensor 150 may have a
portion disposed within the exhaust system 190, such as a tip of
the sensor 150 may extend into a portion of the exhaust system 190.
In other implementations, the sensor 150 may receive exhaust gas
through another conduit, such as a sample pipe extending from the
exhaust system 190. While the sensor 150 is depicted as positioned
downstream of the SCR catalyst 106, it should be understood that
the sensor 150 may be positioned at any other position of the
exhaust system 190, including upstream of the DPF 102, within the
DPF 102, between the DPF 102 and the decomposition chamber 104,
within the decomposition chamber 104, between the decomposition
chamber 104 and the SCR catalyst 106, within the SCR catalyst 106,
or downstream of the SCR catalyst 106. In addition, two or more
sensor 150 may be utilized for detecting a condition of the exhaust
gas, such as two, three, four, five, or size sensor 150 with each
sensor 150 located at one of the foregoing positions of the exhaust
system 190.
III. Implementations of Systems and Methods for Catalyst Failure
Detection
[0031] FIG. 2 depicts a graphical diagram 200 of values for an
NH.sub.3 slip indicator 210, 220, ANR 212, 222, deNO.sub.x
conversion inefficiency 214, 224, and ACN 216, 226 for an
operational SCR catalyst (210, 212, 214, 216) and a failed SCR
catalyst (220, 222, 224, 226). In some implementations, the values
can be acquired during a federal testing procedure (FTP) cycle, a
ramped modal cycle supplemental emissions test (RMCSET), or any
other period of time during engine operations.
[0032] As shown in FIG. 2, when an SCR catalyst is operating
normally and has not failed, the value for a NH.sub.3 slip
indicator 210 remains at a low value. When the SCR catalyst has
failed, such as due to reduced or ceased operation, then the
NH.sub.3 slip indicator 220 may increase during operation due to
NH.sub.3 flowing downstream of the SCR catalyst without reducing
NO.sub.x compounds. In some implementations, the NH.sub.3 slip may
be measured by one or more sensors, such as sensor 150 of FIG. 1,
downstream of at least a portion of the SCR catalyst. In some
instances, two NH.sub.3 sensors may be provided in the exhaust
system. In some instances, the NH.sub.3 slip may increase simply
because the SCR catalyst has failed and the NH.sub.3 in the exhaust
system has not reduced the NO.sub.x compounds in the exhaust gas
when the NH.sub.3 sensor measures the NH.sub.3 concentration within
the exhaust gas. In some cases, the NH.sub.3 slip may increase due
a NO.sub.x sensor detecting NO.sub.x compounds downstream of at
least a portion of the SCR catalyst and a controller, such as
controller 120 of FIG. 1, increasing an amount of ammonia dosed
responsive to the increased detected NO.sub.x The increased amount
of dosed ammonia may result in increased NH.sub.3 slip due to the
reduced operation or failure of the SCR catalyst.
[0033] As shown in FIG. 2, when an SCR catalyst is operating
normally and has not failed, the value for ANR 212 remains near a
constant value. When the SCR catalyst has failed, such as due to
reduced or ceased operation, then the ANR value 222 may increase or
fluctuate during operation. The value for the ANR is a filtered
value of an ANR parameter from a controller, such as controller 120
of FIG. 1. The ANR parameter may be a ANR command value that is
determined based on a feedback control algorithm of the controller.
In some implementations, the value for the ANR is indicated as by a
parameter, such as parameter A. The filtered ANR value is a value
indicative of a ratio of ammonia to NO.sub.x compounds present
within the exhaust system. The ANR value may be a value upstream or
downstream of the SCR catalyst. If the ANR value is high, then the
SCR catalyst may have failed. The high value for ANR may be a
result of a downstream NO.sub.x sensor detecting a high NO.sub.x
concentration downstream of at least a portion of the SCR catalyst,
such as due to reduced or ceased operation of the SCR catalyst, and
the controller increasing an ANR commanded value to increase dosing
of reductant (e.g., to produce ammonia) into the exhaust system
upstream of the SCR catalyst. Because the SCR catalyst has reduced
or ceased operation in assisting in the reduction of NO.sub.x
compounds, the increase in a commanded value for ANR can indicate
such a failure. In some implementations, the ANR value may be a
measured ANR value.
[0034] Conversion inefficiency, C, is also used in calculating the
ACN value. The conversion inefficiency can be calculated by the
following:
C = ( 1 - CE CE Target ) .times. 100 ##EQU00002##
where CE is an estimation of the actual system conversion
efficiency and CE.sub.Target is the estimated target conversion
efficiency for the SCR catalyst. The estimation of the actual
system conversion efficiency can be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. The estimation of the target conversion
efficiency for the SCR catalyst may also be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. When an SCR catalyst is operating
normally and has not failed, the value for conversion inefficiency
214 remains near a constant low value, indicating that the
conversion efficiency is generally at the target conversion
efficiency for the given engine operating parameters, environmental
condition parameters, etc. When the SCR catalyst has failed, such
as due to reduced or ceased operation, then the conversion
inefficiency 224 may increase during operation due to the estimated
actual conversion efficiency being less than the estimated target
conversion efficiency. The estimated actual conversion efficiency
and the estimated target conversion efficiency may be parameter
values determined based on a control algorithm of the
controller.
[0035] The three signals--the NH.sub.3 slip indicator 210, 220,
ammonia to NO.sub.x ratio (ANR) 212, 222, and deNO.sub.x conversion
inefficiency 214, 224--can be multiplied together to generate a new
value of ACN 216, 226. That is, ACN=A.times.C.times.N. In some
implementations, enablement conditions must be satisfied before the
NH.sub.3 slip indicator value, ANR value, and deNO.sub.x conversion
inefficiency value are determined to generate a new ACN value. For
instance, the enablement conditions may include an SCR bed
temperature being within a predetermined range or above a
predetermined threshold value (e.g., between 180.degree. C. and
500.degree. C. and/or above 180.degree. C.), an exhaust flow rate
being within a predetermined range or above a predetermined
threshold value, an ANR value being within a predetermined range or
above a predetermined threshold value, etc. If the enablement
conditions are met, then the controller can acquire the NH.sub.3
slip indicator value, ANR value, and deNO.sub.x conversion
inefficiency value to generate the ACN value.
[0036] FIG. 3 depicts an implementation of a controller 300, such
as the controller 120 of FIG. 1, having an enablement circuit 310,
an NH.sub.3 slip circuit 320, an ANR circuit 330, a deNO.sub.x
conversion inefficiency circuit 340, and an ACN circuit 350. The
enablement circuit 310 is configured to determine if one or more
enablement conditions are met. Determining whether the enablement
conditions are met may include acquiring (e.g., via accessing,
identifying, receiving, and/or determining) one or more values for
parameters indicative of one or more operating conditions. For
instance, the enablement conditions may include an SCR bed
temperature being within a predetermined range or above a
predetermined threshold value (e.g., between 180.degree. C. and
500.degree. C. and/or above 180.degree. C.), an exhaust flow rate
being within a predetermined range or above a predetermined
threshold value (e.g., above a predetermined cfm), an ANR value
being within a predetermined range or above a predetermined
threshold value (e.g., an ANR value between 0.5 and 1.05 and/or
below 1.0), etc. The enablement circuit 310 may receive one or more
engine operating conditions to be used to calculate one or more
values, such as an ANR value based on the engine operating
conditions. In some implementations, the enablement circuit 310 may
also receive an SCR bed temperature value from a temperature sensor
and/or as a parameter from a feed-forward calculation. The
enablement circuit 310 may further receive the exhaust flow rate
value from a flow sensor and/or as a parameter from a feed-forward
calculation. If the enablement conditions are met by the enablement
circuit 310 determination, then the controller 300 may activate the
NH.sub.3 slip circuit 320, the ANR circuit 330, the deNO.sub.x
conversion inefficiency circuit 340, and the ACN circuit 350.
[0037] In one embodiment, the enablement circuit 310 may include or
be communicably coupled with one or more sensors and/or other
circuits of the controller 300 for receiving one or more values
indicative of engine operating conditions. For instance, the
enablement circuit 310 may be coupled to an engine speed sensor for
receiving a value indicative of the speed of the engine, a fuel
flow rate sensor for receiving a value indicative of the fuel flow
rate to the engine, an air flow rate sensor for receiving a value
indicative of an air flow rate, an air temperature sensor for
receiving a value indicative of an air temperature, etc. In some
implementations, the enablement circuit 310 may be communicatively
coupled to one or more other circuits of the controller 300 to
receive engine operating conditions, such as a feedforward circuit
for determining one or more engine operating conditions. In another
embodiment, the enablement circuit 310 may include communication
circuitry including, but not limited to, wired and wireless
communication protocol to facilitate reception of the one or more
values. In still another embodiment, the enablement circuit 310 may
include machine-readable media stored by the memory and executable
by the processor, wherein the machine-readable media facilitates
performance of certain operations to receive the values indicative
of the engine operating conditions. For example, the
machine-readable media may provide an instruction (e.g., command,
etc.) to one or more sensors operatively coupled to the engine to
monitor and acquire data. In this regard, the machine-readable
media may include programmable logic that defines the frequency of
acquisition of the data of the sensors. In yet another embodiment,
the enablement circuit 310 may include any combination of
machine-readable content, communication circuitry, and the one or
more sensors.
[0038] The NH.sub.3 slip circuit 320 calculates and/or determines
the NH.sub.3 slip. In some implementations, the NH.sub.3 slip may
be measured by one or more sensors, such as the sensor 150 of FIG.
1, positioned relative to the exhaust system to detect an amount of
NH.sub.3 slip downstream of at least a portion of the SCR catalyst.
In some instances, two NH.sub.3 sensors may be provided in the
exhaust system. In other implementations, the NH.sub.3 slip may be
determined by the NH.sub.3 slip circuit 320 through a feed-forward
calculation based on the engine operating conditions.
[0039] In one embodiment, the NH.sub.3 slip circuit 320 may include
or be communicably coupled with the one or more sensors and/or
other circuits of the controller 300 for receiving one or more
values indicative of a measured NH.sub.3 amount in the exhaust
system. In some implementations, the NH.sub.3 slip circuit 320 may
be communicatively coupled to one or more other circuits of the
controller 300 to receive values indicative of NH.sub.3 amounts,
such as a feedforward circuit for determining the NH.sub.3 slip
amount. In another embodiment, the NH.sub.3 slip circuit 320 may
include communication circuitry including, but not limited to,
wired and wireless communication protocol to facilitate reception
of the one or more values. In still another embodiment, the
NH.sub.3 slip circuit 320 may include machine-readable media stored
by the memory and executable by the processor, wherein the
machine-readable media facilitates performance of certain
operations to receive the values indicative of the NH.sub.3 slip
amount. For example, the machine-readable media may provide an
instruction (e.g., command, etc.) to one or more NH.sub.3 sensors
operatively coupled to the exhaust system to monitor and acquire
data. In this regard, the machine-readable media may include
programmable logic that defines the frequency of acquisition of the
data of the sensors. In yet another embodiment, the NH.sub.3 slip
circuit 320 may include any combination of machine-readable
content, communication circuitry, and the one or more sensors.
[0040] The ANR circuit 330 calculates and/or determines the ANR. In
some implementations, the value for the ANR is a filtered value of
an ANR parameter used by the controller 300 for controlling dosing
of reductant. The ANR parameter may be a ANR command value that is
determined based on a feedback control algorithm of the controller.
The ANR value may be a value upstream or downstream of the SCR
catalyst. In other implementations, the ANR value may be measured
by one or more sensors upstream and/or downstream of at least a
portion of the SCR catalyst. In some instances, NH.sub.3 and/or
NO.sub.x sensors may be provided in the exhaust system to be used
in the calculation of the ANR value. In other implementations, the
ANR value may be determined by the ANR circuit 330 through a
feed-forward calculation based on the engine operating
conditions.
[0041] In one embodiment, the ANR circuit 330 may include or be
communicably coupled with the one or more sensors and/or other
circuits of the controller 300 for receiving one or more values to
determine the ANR in the exhaust system. In some implementations,
the ANR circuit 330 may be communicatively coupled to one or more
other circuits of the controller 300 to receive values indicative
of ANR amount, such as a feedforward circuit for determining the
ANR amount. In another embodiment, the ANR circuit 330 may include
communication circuitry including, but not limited to, wired and
wireless communication protocol to facilitate reception of the one
or more values. In still another embodiment, the ANR circuit 330
may include machine-readable media stored by the memory and
executable by the processor, wherein the machine-readable media
facilitates performance of certain operations to receive the values
indicative of the ANR amount. For example, the machine-readable
media may provide an instruction (e.g., command, etc.) to one or
more NH.sub.3 and/or NO.sub.x sensors operatively coupled to the
exhaust system to monitor and acquire data. In this regard, the
machine-readable media may include programmable logic that defines
the frequency of acquisition of the data of the sensors. In yet
another embodiment, the ANR circuit 330 may include any combination
of machine-readable content, communication circuitry, and the one
or more sensors.
[0042] The deNO.sub.x conversion inefficiency circuit 340
calculates the deNO.sub.x conversion inefficiency of the system.
The conversion inefficiency calculated by the deNO.sub.x conversion
inefficiency circuit 340 by:
C=(1-CE/CE.sub.Target).times.100
where CE is an estimation of the actual system conversion
efficiency and CE.sub.Target is the estimated target conversion
efficiency for the SCR catalyst. The estimation of the actual
system conversion efficiency can be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. The estimation of the target conversion
efficiency for the SCR catalyst may also be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. In other implementations, the conversion
efficiency, CE, may be based on a measured value of NO.sub.x by a
NO.sub.x sensor upstream and a NO.sub.x sensor downstream of at
least a portion of the SCR catalyst.
[0043] In one embodiment, the deNO.sub.x conversion inefficiency
circuit 340 may include or be communicably coupled with the one or
more sensors and/or other circuits of the controller 300 for
receiving one or more values to determine the deNO.sub.x conversion
inefficiency of the exhaust system. In some implementations, the
deNO.sub.x conversion inefficiency circuit 340 may be
communicatively coupled to one or more other circuits of the
controller 300 to receive values indicative of the estimated actual
system conversion efficiency and the estimated target conversion
efficiency, such as a feedforward circuit for determining the
estimated actual system conversion efficiency and estimated target
conversion efficiency. In another embodiment, the deNO.sub.x
conversion inefficiency circuit 340 may include communication
circuitry including, but not limited to, wired and wireless
communication protocol to facilitate reception of the one or more
values. In still another embodiment, the deNO.sub.x conversion
inefficiency circuit 340 may include machine-readable media stored
by the memory and executable by the processor, wherein the
machine-readable media facilitates performance of certain
operations to receive the values indicative of the actual system
conversion efficiency and target conversion efficiency. For
example, the machine-readable media may provide an instruction
(e.g., command, etc.) to one or more NO.sub.x sensors operatively
coupled to the exhaust system to monitor and acquire data. In this
regard, the machine-readable media may include programmable logic
that defines the frequency of acquisition of the data of the
sensors. In yet another embodiment, the deNO.sub.x conversion
inefficiency circuit 340 may include any combination of
machine-readable content, communication circuitry, and the one or
more sensors.
[0044] The ACN circuit 350 receives the NH.sub.3 slip value from
the NH.sub.3 slip circuit 320, the ANR value from the ANR circuit
330, and the deNO.sub.x conversion inefficiency value from the
deNO.sub.x conversion inefficiency circuit 340. The ANR circuit 350
multiplies the NH.sub.3 slip value, ANR value, and deNO.sub.x
conversion inefficiency value to determine an ACN value. The ACN
circuit 350 then compares the ACN value to a predetermined
threshold value, such as a threshold value of 50, 100, 200, etc.
The predetermined threshold value may be based on empirical data
such that a threshold value where 95% of catalysts have failed
above the threshold value. If the ACN value determined by the ACN
circuit 350 is below the predetermined threshold value, then the
ACN circuit 350 can set and/or reset a flag value or status
parameter value indicative of no failure of the SCR catalyst. In
some implementations, the flag value and/or parameter value may be
used by a timer or other component of the controller to delay the
enablement circuit 310 from activating for a predetermined period
of time (e.g., 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24
hours, etc.). If the ACN value determined by the ACN circuit 350 is
above the predetermined threshold value, then the ACN circuit 350
can set a flag value or status parameter value indicative of a
failure of the SCR catalyst. Responsive to the flag value or
parameter value indicating a failure of the SCR catalyst, a warning
lamp may be lit, such as a malfunction indicator lamp (MIL), and/or
other indicators of the failure of the SCR catalyst may be
utilized.
[0045] FIG. 3 depicts an implementation of a process 400 for
detecting the failure of an SCR catalyst that may be implemented by
the controller 300 of FIG. 3. In the implementation shown, the
process 400 includes acquiring the ANR value 402 and the normalized
conversion inefficiency value 404. The ANR value 402 can be
acquired by the ANR circuit 320 of the controller 300 after the
enablement conditions are met as determined by the enablement
circuit 310. Similarly, the normalized conversion inefficiency
value 404 can be acquired by the deNO.sub.x conversion inefficiency
circuit 340 of the controller 300 after the enablement conditions
are met as determined by the enablement circuit 310. The process
400 further includes a delay or alignment 430 for the ANR value 402
and the normalized conversion inefficiency value 404 to be delayed
for a predetermined period of time, such as a thirty second delay.
The delay or alignment 430 may be provided based on a timer
delaying transmittal of the ANR value 402 and the normalized
conversion inefficiency value 404. The process 400 further includes
an NH.sub.3 slip value 408 that can be acquired using the NH.sub.3
slip circuit 320. The NH.sub.3 slip value 408, the delayed ANV
value 402, and the delayed normalized conversion inefficiency value
404 are then combined, such as via multiplication, to result in an
ACN value 410. In other implementations, a delay for one or more
enablement conditions to acquire the NH.sub.3 slip value 408 may be
used instead of the delay or alignment 430.
[0046] FIG. 5 depicts graphical plot examples showing an ACN value
502 over a period of time, a screening delay flag value 504 over
the period of time, the combined ANR value and normalized
conversion inefficiency value 510 over the period of time, and the
NH.sub.3 slip value 516 over the period of time.
[0047] The combined ANR value and normalized conversion
inefficiency value 510 are shown both as originally calculated 512
and when a delay 514, such as a thirty second delay, is applied.
The combined ANR value and normalized conversion inefficiency value
510 may be the value received and/or used by the ANR circuit 330
and the deNO.sub.x conversion inefficiency circuit 340. The ANR
value and normalized conversion inefficiency value may be based on
a feedforward calculation or may be based on a reading from one or
more sensors. The screening flag value 504 represents a flag value
indicative of when the enablement conditions have been met. A first
set of screening flag values are shown as occurring without a delay
and a second set of screening flag values are shown with a delay,
such as the thirty second delay, is applied. As shown in the
Figure, the NH.sub.3 slip value 516 includes a first region 518 of
values where the enablement conditions have been met, but without
any delay, and a second region 520 where the enablement conditions
have been met with the delay applied. The NH.sub.3 slip value 516
may be the value received and/or used by the NH.sub.3 slip circuit
320. The NH.sub.3 slip value 516 may be based on a feedforward
calculation to determine the NH.sub.3 slip amount or the NH.sub.3
slip value 516 may be based on a reading from an NH.sub.3
sensor.
[0048] FIG. 6 depicts an implementation of a process 600 for
detecting and indicating a failure of an SCR catalyst using the ACN
value. The process 600 includes determining that enablement
conditions are met (block 610). Determining whether the enablement
conditions are met may include acquiring (e.g., accessing,
identifying, receiving, and/or determining) one or more values for
parameters indicative of one or more operating conditions. For
instance, the enablement conditions may include an SCR bed
temperature being within a predetermined range or above a
predetermined threshold value (e.g., between 180.degree. C. and
500.degree. C. and/or above 180.degree. C.), an exhaust flow rate
being within a predetermined range or above a predetermined
threshold value (e.g., above a predetermined cfm), an ANR value
being within a predetermined range or above a predetermined
threshold value (e.g., an ANR value between 0.5 and 1.05 and/or
below 1.0), etc. The determination of if the enablement conditions
are met may be performed by the enablement circuit 310 of FIG. 3.
If the enablement conditions are not met, then the process 600 may
end.
[0049] If the enablement conditions are met, then the process 600
includes acquiring an ANR value and a conversion inefficiency value
(block 620). In some implementations, the ANR value may be acquired
by reading a value of an ANR parameter that is determined based on
a feedback control algorithm of the controller. The ANR value may
be a value upstream or downstream of the SCR catalyst. In other
implementations, the ANR value may be measured by one or more
sensors upstream and/or downstream of at least a portion of the SCR
catalyst. In some instances, NH.sub.3 and/or NO.sub.x sensors may
be provided in the exhaust system to be used in the calculation of
the ANR value. In other implementations, the ANR value may be
determined by the ANR circuit 330 through a feed-forward
calculation based on the engine operating conditions. The
conversion inefficiency value can be acquired by reading a value of
a deNO.sub.x conversion inefficiency parameter that is determined
by the controller. The conversion inefficiency is calculated
by:
C = ( 1 - CE CE Target ) .times. 100 ##EQU00003##
where CE is an estimation of the actual system conversion
efficiency and CE.sub.Target is the estimated target conversion
efficiency for the SCR catalyst. The estimation of the actual
system conversion efficiency can be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. The estimation of the target conversion
efficiency for the SCR catalyst may also be based on a feedforward
algorithm using engine operating parameters, environmental
condition parameters, etc. In other implementations, the conversion
efficiency, CE, may be based on a measured value of NO.sub.x by a
NO.sub.x sensor upstream and a NO.sub.x sensor downstream of at
least a portion of the SCR catalyst.
[0050] Based on the acquired ANR value and conversion inefficiency
value, the process 600 includes calculating an A.times.C value
(block 630). In some implementations, the process 600 includes
delaying access of a NH.sub.3 slip value for a predetermined period
of time (block 640). In some implementations, the predetermined
period of time may be a preset time, such as thirty seconds. In
other implementations, the predetermined period of time may be
empirically determined for the type of system implementing the
process 600 (e.g., for different engine models, different usages,
etc). The delaying of access of the NH.sub.3 slip value may be
based on a timing circuit. In other implementations, acquiring the
NH.sub.3 slip value may not be delayed.
[0051] The process 600 includes acquiring the NH.sub.3 slip value
(block 650), either after the delay or without the delay. In some
implementations, the NH.sub.3 slip value may be acquired by
accessing a parameter storing a measured value indicative of the
NH.sub.3 slip by one or more sensors, such as sensor 150 of FIG. 1,
downstream of at least a portion of the SCR catalyst. In some
instances, two NH.sub.3 sensors may be provided in the exhaust
system. In other implementations, the NH.sub.3 slip value may be
acquired by accessing a parameter storing a value determined
through a feed-forward calculation based on the engine operating
conditions.
[0052] The process 600 further includes calculating an ACN value
(block 660). The calculated A.times.C value may be multiplied by
the acquired NH.sub.3 slip value and/or the acquired ANR value,
conversion inefficiency value, and NH.sub.3 slip value may be
directly multiplied together.
[0053] The process 600 further includes indicating a failure of the
SCR catalyst (block 670). The failure of the SCR catalyst may be
determined based on a comparison of the calculated ACN value to a
predetermined threshold value. In some implementations, the
predetermined threshold value may be an empirically determined
value for a corresponding system. Indicating the failure of the SCR
catalyst may include setting a value for a parameter to a value
indicating that the SCR catalyst has failed (e.g., setting
SCRCatalystFail=1), causing a warning lamp to be lit (e.g., a
malfunction indicator lamp (MIL)), and/or other setting any other
indicators that the SCR catalyst has failed. In some
implementations, other processes may be triggered and/or stopped
responsive to determining the SCR catalyst has failed. In some
implementations, indicating a failure of the SCR catalyst may be
responsive to a predetermined number of calculated CAN values
exceeding the predetermined threshold value, such as indicating a
failure of the SCR catalyst if 10 calculated CAN values exceed the
predetermined threshold value.
[0054] The term "controller" encompasses all kinds of apparatus,
devices, and machines for processing data, including by way of
example a programmable processor, a computer, a system on a chip,
or multiple ones, a portion of a programmed processor, or
combinations of the foregoing. The apparatus can include special
purpose logic circuitry, e.g., an FPGA or an ASIC. The apparatus
can also include, in addition to hardware, code that creates an
execution environment for the computer program in question, e.g.,
code that constitutes processor firmware, a protocol stack, a
database management system, an operating system, a cross-platform
runtime environment, a virtual machine, or a combination of one or
more of them. The apparatus and execution environment can realize
various different computing model infrastructures, such as
distributed computing and grid computing infrastructures.
[0055] A computer program (also known as a program, software,
software application, script, or code) can be written in any form
of programming language, including compiled or interpreted
languages, declarative or procedural languages, and it can be
deployed in any form, including as a standalone program or as a
module, component, subroutine, object, or other unit suitable for
use in a computing environment. A computer program may, but need
not, correspond to a file in a file system. A program can be stored
in a portion of a file that holds other programs or data (e.g., one
or more scripts stored in a markup language document), in a single
file dedicated to the program in question, or in multiple
coordinated files (e.g., files that store one or more modules, sub
programs, or portions of code).
[0056] While this specification contains many specific
implementation details, these should not be construed as
limitations on the scope of what may be claimed, but rather as
descriptions of features specific to particular implementations.
Certain features described in this specification in the context of
separate implementations can also be implemented in combination in
a single implementation. Conversely, various features described in
the context of a single implementation can also be implemented in
multiple implementations separately or in any suitable
subcombination. Moreover, although features may be described above
as acting in certain combinations and even initially claimed as
such, one or more features from a claimed combination can in some
cases be excised from the combination, and the claimed combination
may be directed to a subcombination or variation of a
subcombination.
[0057] Similarly, while operations are depicted in the drawings in
a particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results. In certain circumstances, the
separation of various system components in the implementations
described above should not be understood as requiring such
separation in all implementations, and it should be understood that
the described components and systems can generally be integrated in
a single product or packaged into multiple products embodied on
tangible media.
[0058] As utilized herein, the terms "substantially" and similar
terms are intended to have a broad meaning in harmony with the
common and accepted usage by those of ordinary skill in the art to
which the subject matter of this disclosure pertains. It should be
understood by those of skill in the art who review this disclosure
that these terms are intended to allow a description of certain
features described and claimed without restricting the scope of
these features to the precise numerical ranges provided.
Accordingly, these terms should be interpreted as indicating that
insubstantial or inconsequential modifications or alterations of
the subject matter described and claimed are considered to be
within the scope of the invention as recited in the appended
claims. Additionally, it is noted that limitations in the claims
should not be interpreted as constituting "means plus function"
limitations under the United States patent laws in the event that
the term "means" is not used therein.
[0059] The terms "coupled," "connected," and the like as used
herein mean the joining of two components directly or indirectly to
one another. Such joining may be stationary (e.g., permanent) or
moveable (e.g., removable or releasable). Such joining may be
achieved with the two components or the two components and any
additional intermediate components being integrally formed as a
single unitary body with one another or with the two components or
the two components and any additional intermediate components being
attached to one another.
[0060] The terms "fluidly coupled," "in fluid communication," and
the like as used herein mean the two components or objects have a
pathway formed between the two components or objects in which a
fluid, such as water, air, gaseous reductant, gaseous ammonia,
etc., may flow, either with or without intervening components or
objects. Examples of fluid couplings or configurations for enabling
fluid communication may include piping, channels, or any other
suitable components for enabling the flow of a fluid from one
component or object to another.
[0061] It is important to note that the construction and
arrangement of the system shown in the various exemplary
implementations is illustrative only and not restrictive in
character. All changes and modifications that come within the
spirit and/or scope of the described implementations are desired to
be protected. It should be understood that some features may not be
necessary and implementations lacking the various features may be
contemplated as within the scope of the application, the scope
being defined by the claims that follow. In reading the claims, it
is intended that when words such as "a," "an," "at least one," or
"at least one portion" are used there is no intention to limit the
claim to only one item unless specifically stated to the contrary
in the claim. When the language "at least a portion" and/or "a
portion" is used the item can include a portion and/or the entire
item unless specifically stated to the contrary.
* * * * *