U.S. patent application number 16/382990 was filed with the patent office on 2019-08-08 for radio frequency system and method for monitoring engine-out exhaust constituents.
This patent application is currently assigned to CTS Corporation. The applicant listed for this patent is CTS Corporation. Invention is credited to Leslie Bromberg, Andrew D. Herman, Paul A. Ragaller, Alexander G. Sappok.
Application Number | 20190242288 16/382990 |
Document ID | / |
Family ID | 58578994 |
Filed Date | 2019-08-08 |
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United States Patent
Application |
20190242288 |
Kind Code |
A1 |
Sappok; Alexander G. ; et
al. |
August 8, 2019 |
Radio Frequency System and Method for Monitoring Engine-Out Exhaust
Constituents
Abstract
A radio frequency system and method for monitoring an engine-out
exhaust emission constituent. The system comprises a housing
containing the emission constituent, one or more radio frequency
sensors extending into the housing and transmitting and receiving
radio frequency signals, and a control unit for controlling the
radio frequency signals and monitoring changes in the emission
constituent based on changes in one or more parameters of the radio
frequency signals. In one embodiment, the control unit measures a
rate of change in one or more of the parameters of the radio
frequency signals for monitoring a rate of change of the emission
constituent including for example the emission rate, accumulation
rate, and/or depletion rate of the emission constituent.
Inventors: |
Sappok; Alexander G.;
(Cambridge, MA) ; Ragaller; Paul A.; (Dorchester,
MA) ; Bromberg; Leslie; (Sharon, MA) ; Herman;
Andrew D.; (Granger, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CTS Corporation |
Lisle |
IL |
US |
|
|
Assignee: |
CTS Corporation
Lisle
IL
|
Family ID: |
58578994 |
Appl. No.: |
16/382990 |
Filed: |
April 12, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15481670 |
Apr 7, 2017 |
10260400 |
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16382990 |
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14733525 |
Jun 8, 2015 |
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15481670 |
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14733486 |
Jun 8, 2015 |
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14733525 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 17/309 20150115;
G01N 15/00 20130101; F01N 2560/14 20130101; Y02T 10/24 20130101;
F01N 2560/00 20130101; Y02T 10/12 20130101; F01N 3/208 20130101;
F01N 11/00 20130101; H04W 24/08 20130101; F01N 2560/12 20130101;
B01D 2255/911 20130101; F01N 3/2066 20130101; G01N 22/04 20130101;
B01D 53/9422 20130101; B01D 53/9495 20130101; F01N 3/021 20130101;
H04B 17/18 20150115; F01N 2610/148 20130101 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 3/20 20060101 F01N003/20; H04B 17/18 20060101
H04B017/18; H04W 24/08 20060101 H04W024/08; B01D 53/94 20060101
B01D053/94; H04B 17/309 20060101 H04B017/309; G01N 15/00 20060101
G01N015/00; F01N 3/021 20060101 F01N003/021; G01N 22/04 20060101
G01N022/04 |
Goverment Interests
GOVERNMENT SPONSORSHIP
[0003] This invention was made with government support under Award
No. IIP 1330313 awarded by the National Science Foundation. The
government has certain rights in the invention.
Claims
1. A radio frequency system for monitoring an engine-out exhaust
emission constituent comprising: a housing containing the emission
constituent; one or more radio frequency sensors extending into the
housing and transmitting and receiving radio frequency signals; and
a control unit for controlling the radio frequency signals and
monitoring changes in the emission constituent based on a
measurement of a shift in at least the phase of the radio frequency
signals.
2. The radio frequency system of claim 1, wherein the radio
frequency signals span a radio frequency signal range and the
control unit measures the shift in the phase of the radio frequency
signals in predefined regions of the radio frequency signal
range.
3. The radio frequency system of claim 1, wherein the control unit
measures the shift in the phase of the radio frequency signals in
one or more predefined radio frequency signal ranges corresponding
to one or more predefined spatial regions in the housing.
4. The radio frequency system of claim 1, wherein the control unit
also measures changes in the magnitude or amplitude of the radio
frequency signal.
5. The radio frequency system of claim 4, wherein one or more
emission constituents are monitored by measuring changes in the
magnitude and the shift in the phase of the radio frequency signal
in one or more predefined radio frequency signal ranges.
6. The radio frequency system of claim 1, wherein the control unit
measures a rate of the shift in at least the phase of the radio
frequency signals for monitoring a rate of change of the emission
constituent.
7. The radio frequency system of claim 1, wherein the power
transmitted to the one or more radio frequency sensors is varied to
improve the radio frequency signals.
8. The radio frequency system of claim 6, wherein the control unit
monitors the emission rate, accumulation rate, and/or depletion
rate of the emission constituent.
9. A method for monitoring an emission constituent in a radio
frequency system including a housing containing the emission
constituent, one or more radio frequency sensors extending into the
housing and transmitting and receiving radio frequency signals; and
a control unit, the method comprising the step of controlling the
radio frequency signals and monitoring changes in the emission
constituent based on a measurement of a shift in at least the phase
of the radio frequency signals.
10. The method of claim 9, wherein the radio frequency signals span
a radio frequency signal range and further comprising the step of
measuring the shift in at least the phase of the radio frequency
signals in predefined regions of the radio frequency signal
range.
11. The method of claim 10, further comprising the step of
measuring the shift in at least the phase of the radio frequency
signals in one or more predefined radio frequency signal ranges
corresponding to one or more predefined spatial regions in the
housing.
12. The method of claim 11, wherein the predefined spatial regions
correspond to predefined spatial regions sensitive to the phase of
the radio frequency signal.
13. The method of claim 11, wherein the predefined spatial regions
correspond to predefined spatial regions exhibiting a favorable
behavior for the phase of the radio frequency signal.
14. The method of claim 10, further comprising the step of sampling
the shift in at least the phase of the radio frequency signals in
one or more predefined narrow radio frequency signal ranges to
decrease the measurement response time.
15. The method of claim 14, wherein the one or more predefined
narrow radio frequency signal ranges correspond to one or more
predefined resonant modes of the radio frequency signal.
16. The method of claim 9, further comprising the step of measuring
changes in the magnitude or amplitude of the radio frequency
signal.
17. The method of claim 16, wherein one or more emission
constituents are monitored by measuring changes in the magnitude
and phase of the radio frequency signal in one or more predefined
radio frequency signal ranges.
18. The method of claim 9, further comprising the step of measuring
a rate of the shift in at least the phase of the radio frequency
signals for monitoring a rate of change of the emission
constituent.
19. The method of claim 9, further comprising the step of comparing
the rate of change of the emission constituent with expected values
of the rate of change of the emission constituent.
20. The method of claim 10, further comprising the step of
monitoring the emission rate, accumulation rate, and/or depletion
rate of the emission constituent.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a continuation application of and
claims priority and benefit of the filing date of U.S. patent
application Ser. No. 15/481,670 filed on Apr. 7, 2017, the
disclosure and contents of which is expressly incorporated herein
in its entirety by reference.
[0002] This patent application also claims priority and benefit of
the filing date of and is a continuation-in-part of U.S. patent
application Ser. No. 14/733,525 filed on Jun. 8, 2015 and U.S.
patent application Ser. No. 14/733,486 filed on Jun. 8, 2015, the
disclosure and contents of which are expressly incorporated herein
in their entireties by reference.
FIELD OF THE INVENTION
[0004] This invention relates to a radio frequency system and
method for monitoring engine exhaust emissions constituents in an
internal combustion engine or other process that generates
emissions constituents such, as for example, particulate matter,
gases or liquid constituents.
BACKGROUND OF THE INVENTION
[0005] Various means and methods are used today for monitoring
emissions constituents in the exhaust of an internal combustion
engine such as, for example, gasoline, diesel, natural gas, or
other types of internal combustion engines, that utilize various
emissions after-treatment devices such as an exhaust particulate
filter, for example diesel particulate filters (DPF) and gasoline
particulate filters (GPF), to reduce particulate matter emissions
or various catalysts, traps, and scrubbers to reduce gaseous
emissions, such as selective catalytic reduction systems (SCR), NOX
traps, hydrocarbon traps, ammonia slip catalysts, oxidation
catalysts, three-way catalysts, and the like.
[0006] Indirect methods (utilizing predictive models or so-called
virtual sensors) have been employed to indirectly estimate engine
emissions. These indirect methods have suffered from a number of
shortcomings including for example the fact that these models are
typically developed and calibrated given a specific set of boundary
conditions or system inputs including, but not limited to, engine
characteristics and operating parameters, fuel and lubricant type,
aging factors, safety margins, and the like that require tuning to
a specific set of input conditions which may not be universally
applicable to all engines or systems and thus require some
customization for each end-use application.
[0007] Virtual sensors that rely on these known set of operating
conditions to accurately estimate engine emissions such as, for
example, the composition, amount, rate, or concentration of the
emissions in the exhaust have not by definition functioned
appropriately over conditions or abnormal operation outside the
capabilities of the predictive models.
[0008] Also, changes that occur to the engine as the engine ages
and components wear or break down, or changes that occur to the
catalysts as the catalysts age or become poisoned, cannot be
dynamically captured utilizing predictive models. Generally, safety
factors or deterioration factors are used to compensate for these
changes resulting in a trade-off in overall performance that is
generally too conservative when the engine is new in order to
satisfy the system useful life requirements. The predictive model
approach also suffers from the lack of any feedback mechanism to
directly determine whether the system performance has degraded
beyond the assumed safety margins. Moreover, the development,
calibration, and tuning of the predictive models for a specific
engine and application is time consuming and costly.
[0009] In the case of particulate filters, pressure or differential
pressure sensors have also been used but they suffer from a lack of
resolution and response. In particular, exhaust backpressure or
measurements of the particulate filter differential pressure are
impacted by a wide range of noise factors including exhaust flow
rate, temperature, particulate matter distribution, filter
characteristics (hysteresis effects), and the like. Pressure
measurements also do not provide a direct measure of particulate
matter in the exhaust and lack the resolution to detect particulate
matter build-up on the filter necessary to estimate engine-out PM
emissions rates. Furthermore, pressure measurements are not
reliable overall operating conditions, such as low flow (idle),
with the engine off, during regeneration, or over transient events
for example. This approach, therefore, does not provide a
continuous measurement.
[0010] The use of pressure sensors also typically requires
significant averaging or filtering to reduce the noise effects on
the measurements. This signal averaging or filtering significantly
increases the sensor's response time, making it unsuitable for any
type of meaningful feedback control applications.
[0011] Soot sensors have also been used to measure the
concentration of soot particles in the exhaust. Soot sensors
however have a low measurement range thus resulting in a sensor
that is quickly overwhelmed by the high levels of engine-out soot
emissions. Also, soot sensors are designed to measure very low
concentrations of soot in the exhaust gas stream (after the
particulate filter) and are not suitable for measuring high levels
of engine-out particulate matter emissions. Further, soot sensors
only monitor a portion of the exhaust gas flow, and therefore do
not provide a direct measurement of the total soot levels in the
exhaust gas, but only the levels in the exhaust gas in close
proximity to the sensor (or flowing through the sensor housing).
Soot sensor accuracy is also affected by exhaust flow velocity,
location of the sensing element in the exhaust pipe (as it only
samples a small volume of the flow), temperature, particle
morphology and composition, and accumulation of deposits (ash,
catalyst/washcoat particles) as the sensor ages.
[0012] Accumulation type soot sensors have also been used. These
sensors however do not provide a continuous monitor but rather
cycle from a measuring state to a regeneration state. The
regeneration state generally requires additional energy input to
burn off any accumulated soot on the sensing element. The sensors
also require condensate protection, which does not allow them to
operate during certain conditions, such as cold start for example
when they may be needed most. Accumulation type soot sensors
further do not directly monitor the soot particle number or mass in
the exhaust stream, but rather the time for a certain amount of
material to accumulate on the sensing element, thereby providing
only an indirect indication of soot levels in the exhaust. Soot
sensors also suffer from poor durability, the accumulation of
contaminants (such as ash), as well as thermal shock (water in the
exhaust or condensation), which limits the sensor life and accuracy
over its useful life. Due to the intermittent nature of the sensor
operation which includes regeneration event followed by time period
required for sufficient accumulation to generate a measureable
response, these sensors also do not provide a continuous
measurement.
[0013] A number of different types of gas sensors are also used,
such as for example, NOx sensors, oxygen sensors, ammonia sensors,
and other related sensors, which also suffer from many of the
deficiencies described above. Many of these sensors use
electrochemical cells to conduct the measurements. These types of
sensing elements are fragile and may suffer from a number of
failure modes in the field. In particular, it is well known that
many gas sensors suffer from cross-sensitivities to other exhaust
gas constituents, errors due to variations in the local gas
velocity or flow rate near the sensing element, and
temperature-related effects, among others. These sensors also
sample only a portion of the exhaust flow and not the flow in its
entirety. These sensors may also become poisoned due to
contaminants in fuels, lubricants, or the environment. In another
example, the sensor may become damaged when used in certain
conditions. Many of these sensors also require significant energy
input, such as from heaters, to enable their operation, and may not
function over all operating conditions, such as changes in the
air-fuel ratio in one example, or cold start conditions in
another.
[0014] The present invention provides a direct, accurate, and fast
response measurement of engine exhaust constituent levels using
radio frequency measurements based on the interactions of the
exhaust constituents with the emissions aftertreatment system, and
directly addresses the deficiencies noted above.
[0015] The present invention further provides for a much simpler
and more robust interface to the exhaust system, using only an
antenna to transmit or receive the radio frequency signal to
remotely probe or monitor the aftertreatment system (filter or
catalyst) which itself serves as the sensor.
SUMMARY OF THE INVENTION
[0016] The present invention is directed to a radio frequency
system for monitoring an engine-out exhaust emission constituent
comprising a housing containing the emission constituent, one or
more radio frequency sensors extending into the housing and
transmitting and receiving radio frequency signals, and a control
unit for controlling the radio frequency signals and monitoring
changes in the emission constituent based on changes in one or more
parameters of the radio frequency signals.
[0017] In one embodiment, the radio frequency signals span a radio
frequency signal range and the control unit measures a change in
one or more of the parameters of the radio frequency signals in
predefined regions of the radio frequency signal range.
[0018] In one embodiment, the control unit measures changes in one
or more of the parameters of the radio frequency signals in one or
more predefined radio frequency signal ranges corresponding to one
or more predefined spatial regions in the housing.
[0019] In one embodiment, the control unit measures changes in the
magnitude or amplitude of the radio frequency signal and/or shifts
in the phase of the radio frequency signal.
[0020] In one embodiment, one or more emission constituents are
monitored by measuring changes in the magnitude and/or phase of the
radio frequency signal in one or more predefined radio frequency
signal ranges.
[0021] In one embodiment, the control unit measures a rate of
change in one or more of the parameters of the radio frequency
signals for monitoring a rate of change of the emission
constituent.
[0022] In one embodiment, the power transmitted to the one or more
radio frequency sensors is varied to improve the radio frequency
signals.
[0023] In one embodiment, the control unit monitors the emission
rate, accumulation rate, and/or depletion rate of the emission
constituent.
[0024] The present invention is also directed to a method for
monitoring an emission constituent in a radio frequency system
including a housing containing the emission constituent, one or
more radio frequency sensors extending into the housing and
transmitting and receiving radio frequency signals; and a control
unit, the method comprising the step of controlling the radio
frequency signals and monitoring changes in the emission
constituent based on changes in one or more parameters of the radio
frequency signals.
[0025] In one embodiment, the radio frequency signals span a radio
frequency signal range and further comprising the step of measuring
a change in one or more of the parameters of the radio frequency
signals in predefined regions of the radio frequency signal
range.
[0026] In one embodiment, the step of measuring changes in one or
more of the parameters of the radio frequency signals in one or
more predefined radio frequency signal ranges corresponding to one
or more predefined spatial regions in the housing.
[0027] In one embodiment, the predefined spatial regions correspond
to predefined spatial regions sensitive to the parameter of the
radio frequency signal being measured.
[0028] In one embodiment, the predefined spatial regions correspond
to predefined spatial regions exhibiting a favorable behavior for
the parameter of the radio frequency signal being measured.
[0029] In one embodiment, the step of sampling one or more of the
parameters of the radio frequency signals in one or more predefined
narrow radio frequency signal ranges to decrease the measurement
response time.
[0030] In one embodiment, the one or more predefined narrow radio
frequency signal ranges correspond to one or more predefined
resonant modes of the radio frequency signal.
[0031] In one embodiment, the step of measuring changes in the
magnitude or amplitude of the radio frequency signal and/or shifts
in the phase of the radio frequency signal.
[0032] In one embodiment, one or more emission constituents are
monitored by measuring changes in the magnitude and/or phase of the
radio frequency signal in one or more predefined radio frequency
signal ranges
[0033] In one embodiment, the method further comprises the step of
measuring a rate of change in one or more of the parameters of the
radio frequency signals for monitoring a rate of change of the
emission constituent.
[0034] In one embodiment, the method further comprises the step of
comparing the rate of change of the emission constituent with
expected values of the rate of change of the emission
constituent.
[0035] In one embodiment, the method further comprises the step of
monitoring the emission rate, accumulation rate, and/or depletion
rate of the emission constituent.
[0036] Other advantages and features of the present invention will
be more readily apparent from the following detailed description of
the preferred embodiments of the invention, the accompanying
drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] These and other features of the invention can best be
understood by the description of the accompanying FIGS. as
follows:
[0038] FIG. 1 is a simplified schematic side elevational view of a
vehicle exhaust aftertreatment assembly containing at least one
radio frequency sensor in accordance with the present
invention;
[0039] FIG. 2 is a simplified schematic side elevational view of a
vehicle engine and exhaust system monitored by a radio frequency
system in accordance with the present invention;
[0040] FIG. 3 is a graph representing one radio frequency sensor
based method in accordance with the present invention for
monitoring exhaust emissions;
[0041] FIG. 4A is a graph representing the effect of an emissions
constituent interacting with the filter or catalyst on the
magnitude/amplitude of the radio frequency response over a given
frequency range;
[0042] FIG. 4B is a graph representing the effect an emissions
constituent interacting with the filter or catalyst on the phase of
the radio frequency response over a given frequency range;
[0043] FIG. 5A is a graph representing the change in the measured
emissions constituent accumulation or storage in the particulate
filter or catalyst over time;
[0044] FIG. 5B is a graph representing the derivative of the change
in the measured emissions constituent accumulation or storage in
the particulate filter or catalyst over time;
[0045] FIG. 6A is another graph representing the change in the
measured emissions constituent accumulation or storage in the
particulate filter or catalyst over time; and
[0046] FIG. 6B is a graph representing the rate of change of an
emissions constituent in the particulate filter or catalyst over
time.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0047] The invention relates to a radio frequency based system and
method for monitoring engine-out exhaust emissions constituents as
well as providing feedback control capabilities based on the
monitored emissions.
[0048] For the purposes of this disclosure, the term emissions
constituent refers to any solid, liquid, or gas phase emissions,
whether resulting directly from the upstream process (such as
combustion) as in the case of particulate matter constituents, or
emission constituents introduced into the exhaust system through
the use of additives or dosing, such as hydrocarbon or urea dosing
in one example.
[0049] The terms particulate matter (PM) and soot are used
interchangeably, and refer to particulate matter emission
constituents which may contain carbon, hydrocarbons, sulfates, ash,
or other materials. However, the invention is broadly applicable to
monitoring the rates of emissions constituents in general, in which
case particulate matter may be more broadly defined to include all
types of solid or liquid particles or aerosols, and emissions
constituents further includes any other type of gas or liquid phase
emissions.
[0050] In a particular embodiment, a particulate filter such as a
gasoline particulate filter (GPF) or diesel particulate filter
(DPF) may be installed on a diesel or gasoline engine for any
number of on- or off-road applications.
[0051] In another embodiment, a catalyst, such as a three-way
catalyst (TWC), oxidation catalyst, selective catalytic reduction
system (SCR), NOx trap or LNT, ammonia slip catalyst, hydrocarbon
trap, or any other similar catalyst may be installed. The
applications may include passenger cars, trucks, buses,
construction equipment, agricultural equipment, power generators,
ships, locomotives, and the like. In another example, the filter
may be any type of suitable filter or catalyst installed on any
suitable application.
[0052] FIG. 1 depicts an emissions aftertreatment assembly or
system 102 which, in one example, is a diesel or gasoline
particulate filter assembly that may or may not contain additional
catalysts such as a three-way catalyst, oxidation catalyst,
selective catalytic reduction system, or the like.
[0053] In another example, system 102 is a catalyst such as a
three-way catalyst, oxidation catalyst, selective catalytic
reduction catalyst, NOx trap, or the like and does not contain any
type of filter.
[0054] In yet another example, system 102 contains one or more
catalyst coatings applied to a filter, such as an oxidation
catalyst on a filter, an SCR catalyst applied to a filter, or a TWC
catalyst applied to a filter, or any other catalyst applied to a
filter, forming a so-called multi-function filter.
[0055] Assembly 102 may be comprised of an inlet section 104, a
first module or housing 106, a second module or housing 108, and an
outlet section 110. An inlet conduit 114 is connected to inlet
section 104 and an outlet conduit 116 is connected to outlet
section 110. Inlet and outlet conduits 114 or 116 extend into inlet
and outlet sections 104 or 110 respectively. Inlet and outlet
sections 104 and 110 as well as modules 106 and 108 are connected
via an interconnect 112 including for example a flange, a clamp, or
the like.
[0056] Elements 118 and 120 are contained within modules or
housings 106 and 108, respectively. Although two elements and
modules are shown, multiple configurations are possible, with only
one element and module, or more than one element and module, or
multiple elements contained within a single module. In one
embodiment, elements 118 and 120 are catalysts, filters, membranes,
or some combination thereof.
[0057] In one example, element 118 is an oxidation catalyst, SCR
catalyst, LNT or three-way catalyst, and element 120 is a gasoline
or diesel particulate filter. Additional elements 122, such as
baffles, passages, mixing plates or tubes, and the like, are
contained within one or more sections, or modules. In one
embodiment, the element 122 is a baffle or flow distribution plate.
In another embodiment, element 122 is a radio frequency screen or
mesh. When the element 122 is a radio frequency screen or mesh, it
can be located either upstream in the assembly 102 and the module
106 as shown in FIG. 1, downstream in the assembly 102 and the
module 108, or between the two modules 106 and 108.
[0058] The aftertreatment assembly 102 further comprises additional
structures, probes, sensors, or other elements 124, 126, 128, 130,
132, or 134 extending into the interior of modules or housings 106
or 108 or inlet or outlet sections 104 or 110. In one embodiment,
the additional structures 124, 126, 128 comprise temperature
sensors and the additional structures 128 or 132 comprise oxygen
sensors, NOx sensors, soot sensors, ammonia sensors, pressure
sensors, or the like.
[0059] Probe 134 is a radio frequency measurement probe, such as a
rod antenna loop antenna or waveguide, including dielectric
waveguides, launchers and resonators that are robust and
well-suited to harsh environment applications. Probe 134 is
configured to transmit and receive radio frequency signals
sufficient to generate one or more resonant modes within the
assembly 102 or over any frequency range or ranges. One or more
probes 134 may be used. Probe 134 can be located in several
locations in the assembly 102 such as for example, upstream of the
element 118, downstream of the element 120, between the elements
118 and 120, or even inside the elements 118 or 120. When multiple
probes 134 are located in the assembly 102, they can be located in
the same or different elements 118 and 120 and adapted to monitor
the processes occurring in elements 118 and/or 120 and/or the
processes occurring within the volume defined by the assembly 102
or a region of the assembly 102.
[0060] In another embodiment, probe 134 is a multi-function sensor
including for example a combined radio frequency probe/sensor and
temperature sensor. Probe 134 may also contain multiple integrated
sensors such as for example temperature sensors, pressure sensors,
chemical sensors, and/or particle sensors.
[0061] The radio frequency response of cavity assembly 102 is
influenced by the geometry of the modules 106 and 108, the inlet
and outlet sections 104 and 110 and the inner conducting elements,
probes, sensors, and the like 122, 124, 126, 128, 130, 132, as well
as the interconnects 112.
[0062] Interconnects 112 maintain structural stability to the
assembly 102, seal the assembly 102 against leaks, and provide good
electrical contact between the modules 106 and 108. Clamps or other
shunting elements can be used to provide good electrical contact
between the modules 106 and 108. The type of elements 118 and 120,
as well as their position within modules 106 and 108, respectively,
may also influence the radio frequency measurements. The geometry,
location and mounting of the probe(s) 134 as well as the operation
of a radio frequency control unit including attached cabling (not
shown), may also affect the measurements.
[0063] The mesh 122 is in electrical contact with the assembly 102
and may be placed at different locations within the assembly 102 to
shield or contain the radio frequency signal to a particular region
of the assembly 102. In one embodiment, the mesh 122 may be placed
between the elements 118 and 120, or between the element 120 and
the outlet section 110 in order to isolate the radio frequency
signal to probe filter or catalyst element 120 only. The mesh 122
may be a standard baffle, mixer or flow distribution plate, serving
a number of purposes.
[0064] The mesh 122 or other suitable conducting element may be
used to preferentially control or influence the electric field
distribution within the assembly 102 such as for example to
suppress or enhance selected resonant modes. The mesh 122 or other
suitable conducting elements may be fixed, or variable. In one
example, the mesh 122 or other conducting element may be used to
enhance the resonant modes occurring on either element 118 or 120.
In another example the mesh 122 or other conducting element may be
used to suppress resonant modes or contain the field to only
certain regions within cavity 120 to reduce the effect or external
variables or noise sources on the measurements. The mesh or
conducting element may serve more than one purpose. In one example
the mesh or conducting element functions as a baffle, mixer, or
flow distribution device, in addition to preferentially affecting
the radio frequency signal.
[0065] The radio frequency probe 134 is used to monitor the radio
frequency response of the assembly 102. The radio frequency
response may consist of the radio frequency signal magnitude and/or
phase. The frequency range utilized for the measurements may be any
frequency range, and may or may not result in the establishment of
resonance within cavity 102.
[0066] In one example, the frequency range may include multiple
resonant modes, with each mode corresponding to a specific spatial
or localized region of high electric field strength within the
cavity 102. The radio frequency response to material accumulation
in the cavity 102 is most sensitive to material accumulated in
regions where the electric field is strongest. In one example,
multiple resonant modes may be used to monitor the local loading
state of the filter or catalyst. In another example, multiple
resonant modes may be used to ensure the entire filter or catalyst
volume is sampled to determine the total or aggregate change in
filter loading. In this manner, the radio frequency sensing system
monitors the entire exhaust stream and its interaction with the
filter or catalyst.
[0067] FIG. 2 shows a plant comprising for example an engine and
exhaust system monitored by a radio frequency system. The plant may
be any type of plant, such as a chemical plant, food processing
plant, power plant, refinery, distillery, or any type of plant or
process. The plant or reactor may be a flowing reactor, or it could
be a batch reactor. A machine 202, such as an engine in one example
or a plant in another example, has an outlet connection such as for
example a conduit 206 connected to various components and sensors.
Machine 202 generates an output stream, such as an exhaust stream,
or any other stream, which is directed through conduit 206. In one
embodiment, conduit 206 is connected to a first module 208 and a
second module 210. In one embodiment, modules 208 and 210 may be
cavities, such as resonant cavities, or may be waveguides in
another embodiment.
[0068] In one particular embodiment, module 208 may be a
particulate filter assembly such as the assembly 102 shown in FIG.
1 containing multiple elements such as for example a catalyst
element 212 such as for example a three-way catalyst (TWC),
oxidation catalyst (OC), selective catalytic reduction catalyst
(SCR), lean NOx trap (LNT), or any type of catalyst, and a filter
element 214 such as a particulate filter.
[0069] In one embodiment, module 210 is a catalyst housing
containing a catalyst element 216 such as an SCR, LNT, TWC, ammonia
storage, hydrocarbon trap, scrubber or any other type of
catalyst.
[0070] In another embodiment, no modules 208 or 210 may be present
and, in another embodiment, more than two modules 208 and 210 may
be present. Each of the modules 208 and 210 may contain one or more
elements, such as catalysts, filters or membranes in one example,
or no internal elements in another example.
[0071] Conduit 206 contains one or more internal elements 218 such
as a filter, catalyst, mixer, diffuser, or other element. The
elements 218 may be located at any position within conduit 206.
Radio frequency probes or sensors 220, 222, 224, and 226 such as
rod antennas, loop antennas, waveguides, dielectric resonators, or
any other suitable probes or sensors for transmitting and/or
receiving radio frequency signals are mounted to and extend into
conduit 206 and the modules 208 and 210.
[0072] Additional conduits 232 are connected to machine 202
including for example intake ducts, fuel lines, oil lines, coolant
lines, or other similar conduits. Conduit 232 may supply an inlet
stream to the plant or machine 202. Conduit 232 contains
turbomachinery 230 including for example a turbocharger or
supercharger. An exhaust gas recirculation (EGR) circuit 234 forms
a fluid path between exhaust conduit 206 and inlet conduit 232. The
EGR circuit 234 contains a valve 236 or other suitable flow control
mechanism or actuator for regulating the exhaust flow. EGR circuit
234 may be either high or low pressure, internal or external, and
may be cooled. The inlet conduit 232 contains a throttle or valve
228 for regulating intake flow.
[0073] Machine 202, if in the form of an engine, may contain one or
more cylinders. Fuel may be supplied to the cylinders of machine
202 by means of a fuel delivery system 238 that can include a fuel
supply tank, pumps, and injectors (not shown). The fuel supply
system 238 is mechanically or electronically controlled by means of
a control unit 204.
[0074] Although FIG. 2 depicts machine 202 as having one inlet
conduit 232 and one outlet conduit 206, machine 202 may contain
multiple or no inlet and outlet conduits. Each of the conduits 232
and 206 may consist of a network for connections, passages and
conduits (not shown) such as a pipe or duct system or network
consisting of interconnected conduits of varying sizes and
geometries. Additional modules, such as multiple modules 208, 210,
or 218, may or may not be present in inlet our outlet conduits.
[0075] Emission constituent dosing or injection devices, such as a
doser 240 is present in the machine 202. In one embodiment, the
doser 240 is a hydrocarbon doser for injection hydrocarbons used to
initiate regeneration of the particulate filter 208. In another
embodiment, the fuel injection system 238 is used to perform the
same function. In another embodiment, doser 240 may be a urea doser
or gaseous ammonia injector for supplying urea or ammonia to an SCR
catalyst. Doser 240 may be positioned anywhere along the exhaust
conduit. In one example where module 210 is an SCR catalyst, doser
240 may be a urea doser positioned in conduit 206 upstream of
module 201 but downstream of module 208. In another example, doser
240 may be a hydrocarbon doser positioned upstream of the
particulate filter.
[0076] Radio frequency probes 220, 222, 224, and 226 are connected
to the engine control unit 204. A single or multiple control units
204 may be used to monitor and control all of the radio frequency
probes. Additional sensors not shown, such as temperature sensors,
pressure sensors, gas composition sensors (NOx, PM, Oxygen,
Ammonia) or any other types of sensors may be used. These ancillary
sensors may be connected to the control unit 204 or another control
unit, such as an engine, plant, or process control unit, also not
shown, which may be in communication with control unit 204.
[0077] Control unit 204 includes a processing unit and computer
readable storage medium 242 that contains instructions, algorithms,
data, lookup tables, and any other information necessary to control
the connected sensors and machine. Control unit 204 also includes
connections 244 and 246 comprising a communication connection, such
as Ethernet, USB, analog, CAN, serial, or some other type of
connection, wireless, or power connection. Connection 246 may be
connected to the plant control unit, to the engine control unit
(ECU) in a vehicle, or to signal to the operator of the status of
the control unit and of potential problems.
[0078] Control unit 204 includes hardware or electronics for
transmitting radio frequency signals, such as an oscillator or
synthesizer, as well as a detector for detecting radio frequency
signals such as a diode or power detector or any other type of
detector. Control unit 204 may further contain mixers, splitters,
directional couplers, switches, and other components for
controlling, modulating, transmitting, and monitoring radio
frequency signals. In another example, control unit 204 may be a
network analyzer or spectrum analyzer.
[0079] Control unit 204 is configured to transmit and receive and
control radio frequency signals through any of the radio frequency
probes 220 222, 224, and 226. Each probe may be independently
controlled to transmit, receive, or transmit and receive radio
frequency signals, such as in a multi-port network including
transmission, reflection, and transmission or reflection.
[0080] Control unit 204 is also configured to monitor changes in
one or more of the emission constituents based on changes in one or
more parameters of the radio frequency signals as discussed in more
detail below.
[0081] Control unit 204 may further be configured to modify the
operation of the engine, machine, or emissions after treatment
system based on the radio frequency measurements and, more
specifically based on changes in one or more of the parameters of
the radio frequency signals. Examples of modifications to system
operation include the triggering of fault conditions or changes to
the engine operation, such as fueling, airflow, boost pressure, or
any other process control parameter.
[0082] The radio frequency signals may span a frequency range to
establish one or more resonant modes, or may span a frequency range
that does not include a resonant mode, or may be at a single
frequency or multiple discrete frequencies. The various modules
208, 210, and conduit 206 may serve as microwave resonant cavities
or waveguides, or may contain resonators (such as dielectric
resonators) that can be used to sample a limited region of the
device being monitored.
[0083] The radio frequency signal, including resonance curve,
absolute amplitude, relative amplitude (i.e., normalized to the
power being transmitted by the probe), phase, resonant frequency
shift, frequency shift, or some derivative thereof including local
or absolute maxima or minima, frequency shift at resonance or away
from resonance (such as a notch), phase shift, average value,
quality factor, summation, area, peak width, or other parameter may
be correlated to the state of the system and used by the control
unit 204 to monitor changes in the loading state of the system.
[0084] In one method of operation of the system 102 and control
unit 204 and as shown in FIG. 3, the radio frequency signal may
span a broad frequency range sufficient to generate one or more
resonant modes. In another embodiment, only certain regions of the
broad frequency range may be sampled such as for example the
regions generally designated as regions (A), (B), (C), and (D) in
FIG. 3. The regions of interest may be pre-defined and selected
based on one or more of the following criteria: reduced measurement
time (faster response) by sampling only certain frequency ranges
rather than monitoring the full resonance curve; monitoring only
specific frequency bands, which may correspond to different spatial
locations within the cavity; include only those frequency regions
which are sensitive to the particular parameter being measured
(contaminant material/emissions constituent type); or monitor only
frequency bands which exhibit favorable behavior, such as monotonic
behavior, for the parameter of interest.
[0085] Although the use of a broad frequency range is described,
the range need not be broad. A narrow frequency range or even a
single discrete frequency could also be used in some cases. Several
frequency ranges or single frequencies could be used for a single
measurement, with or without weighting or bias functions in order
to improve the measurement characteristics.
[0086] In another embodiment, one or more narrow frequency ranges
may be used to reduce the sensor response time. The use of narrow
frequency ranges enables hopping between specific frequency bands,
thereby increasing the speed of the measurements. The narrow
frequency bands may correspond to specific resonant modes. Other
means of increasing the measurement response time include reducing
the overall frequency range or decreasing the number of points
sampled across the frequency range.
[0087] In one embodiment, the measurements are conducted with high
resolution at or near specific resonant modes or anti-resonances
(valleys). Decreasing the time required to conduct the measurements
is desirable to enable faster sensor response.
[0088] In another embodiment, only a portion of the resonance curve
is sampled at a particular instance in time, such as regions (A)
and (B) in FIG. 3, with a broader range of the resonance curve or
the full curve sampled at a subsequent point in time.
[0089] In another embodiment, the power transmitted by one or more
of the transmitting elements may be varied to improve the signal
available for measurement. This variation in power output would be
defined by operating conditions. The power output may be variable
using a variable power output synthesizer or oscillator, or through
the addition of an amplifier or attenuator or some other means of
manipulating the power transmitted.
[0090] The radio frequency response may be characterized by the
change in the magnitude and/or phase of the radio frequency signal,
shift in frequency of the signal or any parameter derived or
computed from the radio frequency signal phase, amplitude, or
frequency.
[0091] As shown in FIG. 4A, the effect of an emissions constituent
accumulation in the particulate filter or storage or interaction of
an emission constituent with the catalyst on the
magnitude/amplitude response over a given frequency range relative
to a clean filter or catalyst with no emissions constituent
accumulation is represented by the two resonance states/curves (A)
and (B) respectively. The changes to the resonance states (A) and
(B) depend on the dielectric properties of the contaminant material
as well as the material or media with which it interacts or
displaces. The change in the resonance state shown in FIG. 4A may
be to the amplitude or frequency.
[0092] In one example, as in the case of an emission constituent
such as soot or ammonia, the accumulation of soot or ammonia on a
particulate filter or catalyst respectively may result in a
decrease in amplitude/magnitude of the resonance signal or a shift
in the frequency of the resonance signal. In another example, as in
the case of an emission constituent such as ash, the accumulation
of ash on a particulate filter may not affect the amplitude but may
result in only a frequency shift. In yet another example, the
accumulation or storage of oxygen on a three way catalyst may
produce the opposite behavior, resulting in an increase in
amplitude when oxygen is present and a decrease in amplitude for
the oxygen depleted state. Therefore, the specific resonance
response will depend on the nature of the exhaust or emission
constituent material and its interaction with the filter or
catalyst.
[0093] As shown in FIG. 4B, the accumulation of an exhaust
constituent on the filter or catalyst may also result in a shift in
the phase of the radio frequency signal as represented by the
different curves (A) and (B) in FIG. 4B. The monitored phase may be
absolute or relative. One advantage to use of the control unit 204
to monitor phase in addition to or in lieu of monitoring
amplitude/magnitude is the fact that the amplitude signal may
saturate at high particulate filter or catalyst loading levels, or
due to system aging or poisoning, whereas the phase measurement
provides a wider operating range as the phase shift may not suffer
from the same saturation limitation.
[0094] In one example, the phase and/or magnitude/amplitude of the
RF signal may be monitored at one frequency range which may be
predefined to measure one contaminant material/emission
constituent, while the phase and/or magnitude/amplitude of the RF
signal may be monitored at another frequency range which may be
predefined to measure another contaminant material or exhaust
constituent species.
[0095] In a particular example, one type of contaminant material or
exhaust/emission constituent may be monitored using the amplitude
of the RF signal, whereas a second type of contaminant material or
exhaust/emission constituent may be monitored by the phase of the
RF signal.
[0096] In a further particular example, a contaminant material or
exhaust/emission constituent may be monitored by a shift in
frequency of the magnitude or phase of the RF signal.
[0097] In another particular example, different frequency regions
of the magnitude of the RF signal may be used to monitor one or
more emission constituents with a first frequency region of the
magnitude of the RF signal used to monitor one emission constituent
and a second frequency region of the magnitude of the RF signal
used to monitor a second emission constituent.
[0098] In yet another particular example, different frequency
regions of the phase of the RF signal may be used to monitor one or
more emission constituents with a first frequency region of the
phase of the RF signal used to monitor one emission constituent and
a second frequency range of the phase of the RF signal used to
monitor a second emission constituent.
[0099] In yet a further particular example, different RF signal
characteristics may be used to monitor more than one emission
constituent in the same frequency region, such as by monitoring a
change in frequency (shift), change in magnitude, or change in
phase of the RF signal.
[0100] In yet another example, the contaminant material/emission
constituent monitored may be a solid, liquid, or gas-phase
component. In another example, the frequency, amplitude, or phase
measurement or parameter derived therefrom may related to the state
of the catalyst, filter, or cavity such as its aging state,
condition, health, or functionality.
[0101] Either measurement approach, utilizing magnitude/amplitude
measurements, phase measurements, or both may be applied to
determine emission constituent/particulate matter levels in the
particulate filter, as well as monitor the rate of particulate
matter accumulating on the filter or leaving the filter, either by
escaping the filter or from oxidation. The monitored radio
frequency parameter, such as the amplitude, frequency, or phase, or
a parameter derived therefrom may be over any frequency range.
[0102] Similarly, either measurement approach, utilizing magnitude
measurements, phase measurements, or both may be applied to
determine the storage state of a catalyst, as well as monitor the
rate of one or more exhaust constituents being removed from the
catalyst through desorption, consumption, oxidation, or some other
means. The magnitude and/or phase signals may be utilized directly
or some derivative parameter thereof, such as the average, maximum,
minimum, quality factor (Q), frequency shift, phase shift,
integral, or time derivative, may be computed and used to determine
exhaust emission parameters such as for example engine-out
emissions rates, filter or catalyst accumulation levels, rate of
dosing or addition of an exhaust constituent to the exhaust stream
(such as hydrocarbons or urea) or quantity of particulate matter
lost from the filter or other gas or liquid species consumed by or
lost from a catalyst.
[0103] The rate of change in the radio frequency signal may be
calculated based on two or more radio frequency signal measurements
or average over several radio frequency signal measurements. Other
calculations based on current radio frequency signal measurements
and historical radio frequency signal information may be
employed.
[0104] FIGS. 5A and 5B provide examples of rate of change
monitoring of the radio frequency signal with FIG. 5A depicting the
rate of change in the total particulate filter or catalyst loading
level and FIG. 5B depicting the corresponding rate of change
derivative for three different operation regimes (A), (B), and (C).
Regimes (A) and (C) show a lower level of exhaust constituent
accumulation in the particulate filter or catalyst, whereas regime
(B) shows a relatively high level of exhaust constituent
accumulation.
[0105] In one exemplary embodiment, the change in filter
particulate matter loading levels or catalyst storage levels may be
computed and divided by the time (or some indication of relative
time) between two or more radio frequency signal measurements. The
resulting rate of change in the filter loading level or catalyst
loading state may be related to the engine-out soot emissions in
one example, the dosing rate of hydrocarbons or urea in another
example, or the storage rate of oxygen, NOx, ammonia, or some other
exhaust constituent on a catalyst in yet another example.
[0106] In this manner, the change in the radio frequency signal may
be used to directly monitor engine-out soot levels by monitoring
the change in the build-up of particulate matter on the filter, or
monitor or control the rate of dosing of urea by monitoring the
accumulation or storage of ammonia on the SCR catalyst in another
example.
[0107] In yet another example, the engine out emissions rate of
other solid, liquid, or gas phase emissions may similarly be
monitored or controlled by the control unit 204 based on the
determination of their time rate of change of the storage or loss
of these species from the catalyst or filter. In one example, the
change in the radio-frequency signal may be related to the
engine-out soot emissions rate, with the particulate filter serving
as an accumulation engine-out soot sensor probed or monitored by
the radio frequency signal.
[0108] In another example, the change in the radio frequency signal
may be related to the engine-out emissions rate of a gaseous
species or exhaust constituent with the catalyst serving as
engine-out gas sensors probed or monitored by radio frequency
means. The approach therefore utilizes the filter or catalyst as
the sensing element and enables the total or bulk engine-out
emissions rate or exhaust constituent levels to be monitored.
[0109] In yet another example, the monitored rate of change of a
particular exhaust constituent may be used to diagnose the
operation of the system, by comparing the monitored rate of change
with the expected rate of change. In one example, the operation of
an oxidation catalyst may be diagnosed by comparing the monitored
soot oxidation rate or oxidation rate of a particular exhaust
species, with the expected oxidation rate. A slower than expected
oxidation rate may be indicative of a loss in catalyst function or
activity. Similarly, in another example, the catalyst storage
capacity or uptake rate may be monitored, such as for oxygen
storage on a three way catalyst, ammonia storage on an SCR
catalyst, NOx storage on an LNT, or hydrocarbon storage on a
hydrocarbon trap for example. Lower than expected storage rate may
also be indicative of a loss in catalyst activity and used to
diagnose or detect aged, poisoned, or faulty catalysts.
[0110] Monitoring multiple resonances further provides an
indication of the local rate of change in the catalyst storage
state or catalyst processes. In one example, a change in the
location of the local (spatial) storage on the catalyst may
indicate a loss in catalyst functionality locally. In one example,
the location of the stored exhaust species on the catalyst may
shift from being concentrated at the front of the catalyst toward
the back of the catalyst as the catalyst ages or becomes poisoned.
Monitoring this shift in local storage levels provides additional
information on the health of the catalyst and may be used to
diagnose the catalyst or filter operation. In another example, the
shift in local storage levels may be radially, with differences
between the center and periphery.
[0111] In another example, the rate of exhaust constituent storage
may be used by the control unit 204 to diagnose the upstream
processes such as the engine-out emissions. High levels or rates of
storage on the catalyst or filter may indicate high engine-out
emissions such as high soot emissions or high emissions of certain
gas species such as NOx, hydrocarbons, carbon monoxide, or other
gas species.
[0112] In one example, high engine-out NOx rates, determined either
by a monitored high rate of NOx storage on a NOx trap or a high
rate of ammonia consumption on an SCR catalyst, or a high rate of
soot oxidation on a catalyzed particulate filter may be used to
detect or diagnose engine conditions or faults resulting in high
NOx emissions such as a faulty exhaust gas recirculation (EGR)
system, incorrect combustion conditions, and the like. In a similar
manner high engine-out soot emissions rates, detected by a high
rate of soot accumulation on a particulate filter may be used to
diagnose engine faults or malfunctions resulting in high soot
emissions such as an injection system problem, poor combustion,
lack of airflow, EGR malfunctions, and the like.
[0113] In another example, the diagnosed upstream processes need
not be directly related to the engine, but may related to ancillary
systems, such as hydrocarbon dosing systems or urea dosing systems.
In one example, a comparison by the control unit 204 of the RF
monitored rate of ammonia storage on the SCR catalyst with the
expected rate of ammonia storage may be used to determine whether
or not the urea or gaseous ammonia injection system is functioning
properly, or whether the correct quality or urea is being used.
Similarly, the function of a hydrocarbon dosing system may be
monitored by comparing the RF-monitored rate of soot oxidation on a
particulate filter with the commanded hydrocarbon dosing level and
expected soot oxidation rate. In another example, the same
comparison may be used to determine the health of the catalyst.
[0114] The comparison of the monitored rate of change in the RF
measured quantity on the catalyst or filter may be conducted with
expected values from models or simulations, measurements from other
sensors, stored values, such as in a lookup table, or any other
suitable means. The comparison may be made at known operating
conditions, over normal system operation (such as typical drive
cycles or duty cycles characteristic of the application), or
through intrusive testing by commanding a known change or impulse
to the system and monitoring the system response.
[0115] Feedback from the monitored state or health of the filter or
catalyst may also be used to initiate an action such as an alarm or
trigger a fault code. In another example, the action may be used to
compensate for a reduction in performance of the filter or catalyst
system. In one example, the action may be to reduce the emissions
of a specific exhaust constituent. In another example, the action
may be to increase or decrease urea dosing or hydrocarbon dosing,
or to increase the temperature of the system. Any number of actions
may be employed to further diagnose or control, or improve the
performance of the filter or catalyst based on the RF monitored
performance.
[0116] The time response of the measurement defines the temporal
resolution of the system. Response times of less than one second
are readily achieved over a broad frequency range spanning up to 1
GHz and including over one thousand measurement points. Reducing
the frequency range or number of measurement points can be used to
decrease the measurement response time even further. Signal to
noise ratio can be improved by using signal averaging or modifying
the signal power output, such as by using an amplifier or variable
gain, in another example. In yet another example, the signal to
noise ratio may be improved by modifying the frequency range of
operation.
[0117] In another example, the rate of change in the filter loading
level may be related to the rate of soot oxidation on the
particulate filter such as by filter regeneration, and in yet
another example the rate of change in filter loading may be related
to the rate of particulate matter escaping from the filter, such as
from a failed filter.
[0118] In another example, different parameters may be computed
from different resonant modes and, in yet another example, the rate
of change of one or more resonant modes or resonant mode-derived
parameters may be monitored which may or may not be from the same
mode.
[0119] In another embodiment, knowledge of the engine operating
parameters or operating history may be used to refine or improve
the radio frequency signal measurements. In a particular
embodiment, estimates of soot oxidation rates on the particulate
filter, such as from soot oxidation models, or simple lookup tables
based on the exhaust temperature, may be used to correct the radio
frequency-based estimates of engine-out soot emissions levels. In
one example, the amount of soot estimated to have oxidized over a
specific period of time may be added to the radio frequency-based
measurement of the change in particulate filter soot levels,
thereby accounting for passive or active soot oxidation processes.
In another example, the radio frequency measurements may only be
carried out at low exhaust temperature conditions, such as below
three hundred deg. C, or low NOx: PM ratios, where passive soot
oxidation on the particulate filter may be negligible.
[0120] In yet another example, such as may be the case in a
gasoline engine, the measurements may be carried out during
conditions which are unsuitable for soot oxidation, such as
oxygen-depleted conditions, in one example.
[0121] Similarly, the rate of consumption of other gaseous exhaust
constituents may be monitored, such as the reduction of NOx
emissions through the monitored consumption of ammonia on the SCR
catalyst in one example or the oxidation of carbon monoxide or
hydrocarbons through the monitored reduction in stored oxygen on a
three way catalyst in another example. In a further example, the
radio frequency measurements may only be carried out at conditions
favorable for the measurements or conditions which allow for more
accurate measurements of the monitored parameter. Many such
conditions exist. In one example, the monitored rate of ammonia
storage or consumption on the SCR catalyst may be carried out at
low exhaust temperature where ammonia oxidation is negligible or
when exhaust conditions are unfavorable for oxidation. Measurements
may also be carried out at either lean or rich air fuel ratios
which favor certain processes and inhibit others, or at low exhaust
humidity, water, or moisture/condensate levels. In another example,
corrections for one or more noise factors in the signal may be
employed, such as applying a known offset or shift in the measured
value based on knowledge of the system state or presence/absence of
a particular noise factor.
[0122] FIGS. 6A and 6B depict the monitored change in particulate
filter soot levels or catalyst storage or loading levels using
radio frequencies (i) with the rate of change in the emissions
constituent (ii) in reference to three operational regimes (A),
(B), and (C) in which regime (A) corresponds to a high level of a
particular emissions constituent, (B) corresponds to an equilibrium
condition where the accumulation or storage rate of the emissions
constituent on the filter or catalyst is equal to the rate of
consumption, oxidation, or loss of the emissions constituent, and
(C) corresponds to a condition where the rate of the emissions
constituent loss, consumption, or oxidation exceeds the rate of
accumulation. FIG. 6A also depicts the radio frequency response
after application of a correction for the soot oxidation on the
filter or gas species oxidation or loss from the catalyst,
indicated by the curves designated (A*), (B*), and (C*).
[0123] Implementing such an approach to account for soot oxidation
or oxidation or consumption of a particular exhaust or emission
constituent species, such as ammonia in one example, or oxygen in
another example, therefore enables accurate measurements of
engine-out soot emissions, or gas species emissions, or dosing
based on the measured change in particulate filter soot loading
levels, or catalyst storage levels, even for conditions where the
overall soot levels in the filter or gas species on the catalyst
are unchanging or decreasing.
[0124] Measurements from pressure sensors or temperature sensors in
the exhaust system may further be used to correct the radio
frequency signal in another embodiment, and measurements from gas
sensors such as soot, NOx, or ammonia, or oxygen sensors, may be
used to correct the radio frequency measurement in yet another
embodiment. In another example, results of models or simulations,
or stored values may be used to correct the signal.
[0125] In one example, measurements of exhaust temperature and NOx
or oxygen concentrations may be used to infer a soot oxidation rate
and correct the RF sensor measured soot accumulation on the filter
or RF-measured engine-out soot levels in another example. In
another example, the ammonia oxidation rate on an SCR catalyst or
rate of consumption of oxygen on a three way catalyst may be
inferred. In a further example, the correction may be made based on
models or lookup tables and the like. In yet another example, the
measurements from existing exhaust sensors or models (virtual
sensors) may be used to determine conditions where soot oxidation
is negligible or gas species oxidation stored on catalysts is
negligible, and conditions are favorable for highly accurate RF
measurements of soot accumulation rates on the filter or gas
species storage rates on catalysts.
[0126] In another embodiment, measurements of engine-out exhaust
constituents based on the radio frequency signal may further be
used as a plausibility check for engine-out emissions models, or
exhaust species oxidation models. In a particular embodiment, the
radio frequency measurements may be used to improve the accuracy of
engine-out emissions models used for comparison with measurements
from downstream sensors such as soot sensors or ammonia sensors or
NOx sensors for on-board diagnostic applications.
[0127] The engine-out emission constituent levels may be monitored
over the course of normal engine operation. Abnormally high or low
levels of engine-out constituent emissions may be used to diagnose
engine or component failures or malfunctions such as faulty
injectors, dosing system malfunctions, use of incorrect fluids, low
or high EGR rates, intake or turbocharger problems, high oil
consumption, control system problems, exhaust leaks, problems with
the aftertreatment system, and the like.
[0128] In another example, engine operating parameters may be
actively manipulated to generate a known level of engine-out
constituent emissions, the accumulation on the particulate filter
or catalyst thereof, may be detected and monitored by the changes
in the radio frequency signal shown in FIGS. 4, 5, and 6. In one
example, engine fueling, intake air, EGR, boost, injection timing,
urea, ammonia, or hydrocarbon dosing or similar parameters may be
modified to induce a change in the engine-out emissions
constituents. Monitoring the rate of soot accumulation on the
particulate filter or gaseous emissions storage on a catalyst
either during or after such an intrusive test, provides information
to diagnose the state of the filter or engine. The type, duration,
and frequency of such an intrusive test may be fixed, or varied
based on the circumstances. In one particular embodiment, such
intrusive tests may be used for OBD purposes. In another
embodiment, measurements of engine-out emissions determined from
the radio frequency signal, may be used to modify or control the
engine operation, such as the fueling or injection timing in one
example, or the EGR rate or intake airflow in another example, or
urea, ammonia, or hydrocarbon dosing in yet another example.
[0129] In another example, the rate of engine-out emissions
measured by the change in the radio frequency signal may be used to
monitor or diagnose the engine combustion process, or provide a
feedback control loop to the engine combustion process or engine
operation. The engine parameters that may be monitored or diagnosed
include the intake air flow, fuel injection, injection timing,
boost or turbomachinery operation, EGR systems, actuators, other
sensors and control systems, and other parameters.
[0130] It is also possible to control the emissions constituents
from the engine in order to improve the performance of the
particulate filter or catalyst. For example, after a full
regeneration it would be possible to adjust engine soot emissions
in order to condition the filter, for example, establishing the
cake layer on the surfaces of the filter. Monitoring of the filter
is used to control emissions. In addition, it may be possible to
set engine operation in order to adjust the soot characteristics,
for example, by making soot with properties best suited to form the
cake layer and prevent pore filtration, or generating soot with
properties more or less favorable for oxidation in another example.
In one example, the particle size may be controlled. In another
example the particulate matter composition may be controlled
include the soluble organic fraction. Once the filter has been
conditioned, measured by the radio frequency sensing, the engine
operation is returned to normal.
[0131] Similarly, it is also possible to control the constituent
emissions from the engine to improve the performance of catalysts.
In one example, the performance of the SCR catalyst may be improved
through a de-sulfation event or regeneration to remove accumulated
sulfur, which may be triggered based on the radio frequency signal
measurements of catalyst performance. An increase in sulfur
build-up may be detected directly through shifts in the radio
frequency signal or through a reduction in ammonia storage or the
rate of ammonia storage following a predetermined dosing event
based on the local or global aggregate ammonia storage levels or
rate of change in storage levels of ammonia. In another example,
the SCR catalyst may be conditioned by managing the ammonia
inventory to a specific level determined based on the RF
measurements. Other examples include the modulation of air-to-fuel
ration to achieve a specific amount of oxygen storage on a
three-way catalyst. In yet another example, engine-out emissions
may be modified to preferentially influence the catalyst processes
such as soot oxidation (by increasing NOx or oxygen for example) or
periodic rich or lean excursions, such as for passive ammonia
generation in another example. In a particular example, the RF
measurements may be used to control ammonia generation for a
passive SCR system or so-called hydrocarbon SCR system.
[0132] In yet another embodiment, information regarding the engine
operating parameters may be utilized to correct, refine, or
optimize the radio frequency measurements. In a particular example
the engine information includes engine speed, fueling, torque, EGR
rate, intake air flow, and similar parameters.
[0133] The RF measurements of engine-out emissions may be
determined based on the total aggregate change in filter loading
levels or catalyst storage levels or the local change in filter
loading or catalyst storage, based on the response of specific
resonant modes or frequency ranges.
[0134] Numerous variations and modifications of the embodiment
described above may be effected without departing from the spirit
and scope of the novel features of the invention. It is to be
understood that no limitations with respect to the radio frequency
system and method for monitoring engine-out emissions described
herein are intended or should be inferred. It is, of course,
intended to cover by the appended claims all such modifications as
fall within the scope of the claims.
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