U.S. patent application number 14/325528 was filed with the patent office on 2016-01-14 for reduced emissions internal combustion engine systems.
The applicant listed for this patent is Cummins Inc.. Invention is credited to Jennifer Kay Light-Holets.
Application Number | 20160010528 14/325528 |
Document ID | / |
Family ID | 55067230 |
Filed Date | 2016-01-14 |
United States Patent
Application |
20160010528 |
Kind Code |
A1 |
Light-Holets; Jennifer Kay |
January 14, 2016 |
REDUCED EMISSIONS INTERNAL COMBUSTION ENGINE SYSTEMS
Abstract
Internal combustion diesel engine systems and methods of
operation are disclosed that include a diesel engine, an exhaust
gas recirculation system, a wastegated turbocharger, an exhaust
throttle, and a vanadia selective catalytic reduction catalyst
downstream of the exhaust throttle.
Inventors: |
Light-Holets; Jennifer Kay;
(Greenwood, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cummins Inc. |
Columbus |
IN |
US |
|
|
Family ID: |
55067230 |
Appl. No.: |
14/325528 |
Filed: |
July 8, 2014 |
Current U.S.
Class: |
60/274 ; 60/295;
60/599; 60/605.2 |
Current CPC
Class: |
F01N 2610/1453 20130101;
F02D 9/04 20130101; Y02T 10/47 20130101; F01N 2610/02 20130101;
F02M 26/05 20160201; F02B 37/183 20130101; F02B 29/04 20130101;
F02D 41/024 20130101; Y02T 10/12 20130101; Y02T 10/144 20130101;
Y02T 10/24 20130101; F01N 3/208 20130101; Y02T 10/26 20130101; F02D
41/0007 20130101; F02B 37/18 20130101; F02M 26/26 20160201; F02B
29/0418 20130101; F01N 2900/1402 20130101; Y02T 10/40 20130101;
Y02T 10/146 20130101; F01N 2900/1602 20130101; F02D 41/0055
20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F02B 37/18 20060101 F02B037/18; F02M 25/07 20060101
F02M025/07; F02B 29/04 20060101 F02B029/04 |
Claims
1. A method comprising: operating an internal combustion engine to
produce an exhaust gas flow to an exhaust system with a number of
exhaust gas treatment and flow control components consisting
essentially of a vanadia selective catalytic reduction (SCR)
catalyst, an exhaust throttle upstream of the vanadia SCR catalyst,
a turbocharger with a controllable wastegate upstream of the
vanadia SCR catalyst, and an exhaust gas recirculation (EGR)
control valve connected with an EGR conduit connecting the exhaust
system to an intake system to control recirculation of exhaust gas
to the intake system; and reducing NOx in the exhaust gas flow with
the vanadia SCR catalyst by injecting a reductant upstream of the
vanadia SCR catalyst, wherein the exhaust gas flow to the passes
from the exhaust throttle directly to the vanadia SCR catalyst
without an intervening particulate filter or oxidation catalyst
between the exhaust throttle and the vanadia SCR catalyst.
2. The method of claim 1, further comprising: determining at least
one parameter associated with operation of the system that
indicates a NOx output level from the vanadia SCR catalyst, wherein
the NOx output event is caused at least in part by operating
conditions of the vanadia SCR catalyst; and in response to the NOx
output event, initiating a NOx reduction event to reduce an amount
of NOx to the vanadia SCR catalyst by reducing a NOx output by the
internal combustion engine.
3. The method of claim 2, wherein reducing the NOx output includes
closing at least one of the wastegate and the exhaust throttle to
increase an amount of exhaust gas flow recirculated to the intake
system.
4. The method of claim 2, wherein reducing the NOx output includes
at least partially closing each of the wastegate and the exhaust
throttle to increase an amount of exhaust gas flow recirculated to
the intake system.
5. The method of claim 2, wherein reducing the NOx output includes
opening the EGR control valve to increase an amount of exhaust gas
flow recirculated to the intake system.
6. The method of claim 1, further comprising: determining at least
one parameter associated with operating the internal combustion
engine that indicates a temperature condition of the vanadia SCR
catalyst; and in response to the temperature condition being
outside an effective temperature range, initiating a temperature
change event to change a temperature of the vanadia SCR catalyst to
the effective temperature range.
7. The method of claim 6, wherein the temperature change event
includes changing an amount of exhaust gas recirculated to the
intake system.
8. The method of claim 7, wherein the temperature change event
indicates a temperature increase of the vanadia SCR catalyst and
further comprising bypassing an EGR cooler connected to the EGR
conduit to increase a temperature of the exhaust gas flow.
9. The method of claim 6, wherein the temperature change event
includes changing an amount of exhaust gas passing through at least
one of the wastegate of the turbocharger and the exhaust throttle
to change the temperature of the vanadia SCR catalyst.
10. The method of claim 6, wherein the temperature change event
includes changing an amount of exhaust gas passing through the
exhaust throttle to change the temperature of the vanadia SCR
catalyst.
11. The method of claim 6, wherein the temperature change event
includes increasing a temperature condition of the vanadia SCR
catalyst to the effective operating temperature range.
12. A method comprising: operating an internal combustion engine to
produce an exhaust gas flow through an aftertreatment system
including at least one vanadia selective catalyst reduction (SCR)
catalyst and a reductant injector upstream of the vanadia SCR
catalyst, wherein the exhaust gas flow is provided directly to the
vanadia SCR catalyst from a turbine outlet without an intervening
particulate filter and without an intervening oxidation catalyst
upstream of the vanadia SCR catalyst; determining a NOx output in
the exhaust gas flow from the vanadia SCR catalyst; in response to
the NOx output being greater than a NOx output threshold,
initiating a NOx output reduction event to reduce a NOx output by
the internal combustion engine, wherein the NOx output reduction
event includes increasing an amount of recirculated exhaust gas by
at least one operation including closing an exhaust throttle
upstream of the vanadia SCR catalyst, closing a wastegate of the
turbine, and opening an exhaust gas recirculation (EGR) control
valve in an EGR system operable to provide exhaust gas flow to an
intake of the internal combustion engine.
13. The method of claim 12, wherein the at least one operation
includes closing the wastegate of the turbocharger and opening the
EGR control valve.
14. The method of claim 12, wherein the at least one operation
includes closing the exhaust throttle and opening the EGR valve
while the wastegate of the turbocharger is open.
15. The method of claim 12, wherein the exhaust gas flow passes, in
order, through at least one of the wastegate and the turbocharger,
the exhaust throttle and the vanadia SCR catalyst.
16. A system, comprising: an internal combustion engine operable to
receive an intake flow from an intake system and produce an exhaust
gas flow to an exhaust system; a turbocharger including a turbine
in the exhaust system and a compressor in the intake system, the
exhaust system including an aftertreatment system including a
vanadia selective catalytic reduction (SCR) catalyst and a
reductant injector connected to a reductant source upstream of the
vanadia SCR catalyst, the exhaust system further including an
exhaust throttle upstream of the vanadia SCR catalyst and a
wastegate associated with the turbine upstream of the exhaust
throttle, wherein the exhaust throttle receives exhaust gas flow
from the turbine and the wastegate and the vanadia SCR catalyst
receives exhaust flow from the exhaust throttle without an
intervening particulate filter and without an intervening oxidation
catalyst; and an exhaust gas recirculation (EGR) system connecting
the exhaust system to the intake system, the EGR system including
an EGR cooler to cool recirculated exhaust gas flow and an EGR
control valve operable to control an amount of recirculated exhaust
gas.
17. The system of claim 16, wherein the EGR system includes an EGR
bypass around the EGR cooler.
18. The system of claim 17, wherein the EGR control valve is
upstream of the EGR cooler.
19. The system of claim 17, wherein the EGR control valve is
downstream of the EGR cooler.
20. The system of claim 16, wherein the wastegate is an external
wastegate.
21. The system of claim 16, wherein the engine is a diesel
engine.
22. The system of claim 16, wherein the EGR system is connected to
the exhaust system upstream of the turbine.
Description
BACKGROUND
[0001] Internal combustion engines, such as diesel engines, are
connected with exhaust systems that typically include
aftertreatment systems to reduce emissions of pollutants from the
tailpipe, such as NOx. Such aftertreatment systems can employ
oxidation catalysts, particulate filters, and selective catalytic
reduction (SCR) catalysts. Since SCR catalysts typically operate
most efficiently at higher exhaust temperatures, certain exhaust
heating strategies, such as hydrocarbon injection, oxidation
catalysts, and/or variable geometry turbine (VGT) inlet control,
are employed to increase or maintain the temperature of the SCR
catalyst in its effective temperature range. However, these exhaust
heating strategies and NOx emissions control with such systems are
obtained at a high initial system cost, fuel penalties, and/or high
operating costs over the life of the system.
[0002] SCR catalysts are subject to deterioration in performance
resulting from the accumulation of various contaminants, such as
sulphur and hydrocarbons, on the SCR catalyst. In exhaust systems
that include particulate filters, active particulate filter
regeneration can serve in part as a regeneration event for the SCR
catalyst as well to remove sulphur poisoning. However, particulate
filter regeneration results in a fuel penalty, and diesel
particulate filters require servicing and additional expense in
cost and operation of the aftertreatment system. In addition, while
vanadia SCR catalysts provide improved NO conversion and tolerance
to sulphur poisoning than other SCR catalysts, aftertreatment
systems that employ particulate filters typically do not employ
vanadia SCR catalyst due to their lack of thermal durability in
high temperature conditions, such as those that occur during
particulate filter regeneration.
[0003] Diesel engine exhaust systems also raise exhaust gas
temperatures by controlling an opening of an inlet to a variable
geometry turbine (VGT) in the exhaust system. However, VGT's are
expensive and control of the opening can be complicated depending
on engine operating conditions to achieve the desired result.
Therefore, further technological developments are desirable in this
area that provide a low cost exhaust and aftertreatment system for
an internal combustion engine that are operable to meet emissions
standards.
SUMMARY
[0004] Internal combustion engine systems and methods are disclosed
that include an exhaust gas recirculation (EGR) system with an EGR
control valve to control EGR flow from the exhaust system to the
intake system, a turbocharger including a turbine with a wastegate,
an exhaust throttle, and a vanadia SCR catalyst. The system and
methods of operation of the system do not employ a VGT, oxidation
catalyst or particulate filter. Emissions such as NOx are
controlled by controlling engine NOx output levels and/or by
raising or maintaining exhaust temperatures so the vanadia SCR
catalyst is in its effective operating temperature range. Such
operations can be achieved, for example, through control of the EGR
control valve to regulate the amount of recirculated exhaust gas,
control of the wastegate to regulate the amount of the exhaust gas
through the wastegate and the turbine inlet, and control of the
exhaust throttle to control the amount of exhaust gas to the
vanadia SCR catalyst and temperature of the exhaust gas.
[0005] This summary is provided to introduce a selection of
concepts that are further described below in the illustrative
embodiments. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter. Further embodiments, forms, objects, features,
advantages, aspects, and benefits shall become apparent from the
following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic of a system that includes an internal
combustion engine connected to an exhaust system with an EGR
system, wastegated turbocharger, exhaust throttle and a vanadia SCR
catalyst downstream of the exhaust throttle.
[0007] FIG. 2 is a schematic of an alternate arrangement of the EGR
system.
[0008] FIG. 3 is a flow diagram of a procedure for operating the
system of FIG. 1.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0009] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and specific language will
be used to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended, any alterations and further modifications in the
illustrated embodiments, and any further applications of the
principles of the invention as illustrated therein as would
normally occur to one skilled in the art to which the invention
relates are contemplated herein.
[0010] Referring to FIG. 1, there is shown a system 10 that
includes an internal combustion engine 12 that is operable to
produce an exhaust gas flow 14 into an exhaust system 16 connected
to engine 12. The engine 12 may be a diesel engine, either as a
stand-alone power source, in combination with other engines, or
part of a hybrid power train including an internal combustion
engine for at least one of the power sources. System 10 can be used
for mobile applications such with a vehicle, locomotive, or marine
application, or for stationary applications such as a power
generation or pumping system.
[0011] Exhaust system 16 includes at least one exhaust flow path 18
for conveying the exhaust gas to and through an aftertreatment
system 20. System 10 also includes an intake system 70 to provide a
charge flow to engine 12 that includes intake air and recirculated
exhaust gas. A turbocharger 80 is provided that includes a turbine
82 in exhaust flow path 18 and a compressor 84 in intake system 70.
A wastegate 86 is provided at turbine 82 to provide an exhaust flow
path that bypasses turbine 82 in response to certain operating
conditions. In the illustrated embodiment, wastegate 86 is an
external wastegate. Other embodiments contemplate an internal
wastegate.
[0012] Exhaust system 16 further includes an exhaust throttle 74
downstream of turbine 82. Intake system 70 may further include an
intake throttle 72 downstream of compressor 84. An EGR system 90
includes an EGR conduit 94 connecting exhaust flow path 18 to
intake system 70. In the illustrated embodiment, EGR system 90 is a
high pressure system that is connected upstream of turbine 82 and
downstream of compressor 84. EGR system 90 includes an EGR control
valve 92 connected to EGR conduit 94 and an EGR cooler 96. An EGR
bypass 98 is configured to bypass all or a portion of the EGR flow
around EGR cooler 96. In the embodiment of EGR system 90
illustrated in FIG. 1, EGR control valve 92 is upstream of EGR
cooler 96. In another embodiment EGR system 90', such as shown in
FIG. 2, EGR valve 92 is downstream of EGR cooler 96 and/or an EGR
cooler bypass is omitted. Exhaust throttle 74, intake throttle 72,
wastegate 86, and EGR control valve 92 can be controlled by a
controller 50 to facilitate control of the thermal output and/or
NOx output from engine 12.
[0013] Aftertreatment system 20 includes at least one vanadia SCR
catalyst 22 operationally coupled to the at least one exhaust flow
path 18 from engine 12. It is contemplated that exhaust system 16
lacks any variable geometry turbines, oxidation catalysts, and
particulate filters upstream of vanadia SCR catalyst 22, and, as
discussed further below, exhaust throttle 74, wastegate 86, and EGR
control valve 92 are operable to provide engine NOx output
management and thermal management of aftertreatment system 20 to
produce reduced NOx emissions from exhaust system 16 and
temperature control of vanadia SCR catalyst 22.
[0014] Exhaust throttle 74, wastegate 86, and EGR control valve 92
each include an actuator that is operably connected to controller
50 to receive control signals that actuate the respective device to
or between on-off or open-closed positions in response to operating
parameters of engine 12 and the exhaust system 16 to provide NOx
output management from and temperature management of the
aftertreatment system 20. Exhaust throttle 74 and/or EGR control
valve 92 can include any suitable valve member in the exhaust flow
path that is actuatable between at least two positions, such as an
open/on position, and a closed/off position, although full
authority valve members are not precluded. The valve members of
exhaust throttle 74 and/or EGR control valve 92 can be, for
example, a butterfly type valve, a guillotine-type valve, or a
ball-type valve. In one embodiment, the flow restricting portion of
the valve of exhaust throttle 74 includes a passage so that when
the valve is closed or off, a minimum exhaust flow is permitted to
pass therethrough that is set at a targeted low load condition of
engine 12. The actuators can be an electronic actuator, an electric
motor, a pneumatic actuator, or any other suitable type of actuator
to operate the valve member of the exhaust throttle 74, wastegate
86 and EGR control valve 92.
[0015] In one embodiment of system 10, exhaust gas flow 14 passes
in order from at least one of turbine 82 and wastegate 86, directly
to exhaust throttle 74, and then directly to vanadia SCR catalyst
22. Aftertreatment system 20 is designed to operate without
intervening particulate filtration or an oxidation reaction
upstream of vanadia SCR catalyst 22, and omits any particulate
filter and oxidation catalyst upstream of vanadia SCR catalyst 22.
As a result there are no active regeneration events in the
operation of system 10 that are directed to regeneration of a
particulate filter or oxidation reactions upstream of vanadia SCR
catalyst 22, reducing the exposure of vanadia SCR catalyst 22 to
high impact thermal events typically associated with particulate
filter regeneration and oxidation reactions.
[0016] Exhaust aftertreatment system 20 may include a reductant
injector 30 upstream of vanadia SCR catalyst 22 and downstream of
exhaust throttle 74. Reductant injector 30 is supplied with
reductant from a reductant source or reservoir 32 and is operable
to inject reductant into the exhaust gas flow 14 in exhaust flow
path 18. In an exemplary embodiment the reductant is a diesel
exhaust fluid (DEF) such as urea which decomposes to provide
ammonia. Other embodiments utilize different reductants, for
example, aqueous solutions of ammonia, anhydrous ammonia, or other
reductants suitable for SCR operations. Reductant injected into
exhaust flow path 18 is provided to vanadia SCR catalyst 22 which
is in flow communication with exhaust flow path 18 and is operable
to catalyze the reduction of NOx.
[0017] Exhaust flow path 18, as illustrated schematically in FIG.
1, proceeds from the output of engine 12, through a conduit to a
connection of EGR system 90, then to turbine 82, then to exhaust
throttle 74, and then to a structure containing vanadia SCR
catalyst 22 and through another conduit which outlets to the
ambient environment. Certain embodiments may also include an
ammonia oxidation AMOX catalyst 24 at a position downstream of, or
one the downstream side of, the vanadia SCR catalyst 22, which is
operable to catalyze the reaction of NH.sub.3 which slips past the
SCR catalyst 22.
[0018] Engine 12 produces exhaust gas flow 14 by combustion of fuel
provided from fuel source 40 of a fuelling system. Fuel source 40,
in the illustrated embodiment, is connected to a plurality of
cylinders 42 of engine 12 with one or more fuel lines 44. In one
embodiment, the fuel system is provided with a common rail 46 that
distributes fuel to cylinders 42 with one or more injectors (not
shown) at each cylinder 42, which are connected to a common rail 46
of the fuel system. It is further contemplated that any suitable
connection arrangement with fuel source 40, injection location,
and/or injector type can be used to provide fuel directly and/or
indirectly to the combustion chambers of cylinders 42.
[0019] In certain embodiments, the system 10 further includes a
controller 50 structured or configured to perform certain
operations to initiate a temperature change event and/or NOx
reduction event, and control engine operations, EGR operations,
wastegate operations, and exhaust throttle operations to produce an
engine out NOx amount and/or exhaust gas flow temperature that
results in a desired NOx reduction in the engine output and/or
change in temperature of the exhaust gas flow 14. In certain
embodiments, the controller 50 can be an engine control module
and/or forms a portion of a processing subsystem including one or
more computing devices having memory, processing, and communication
hardware. The controller may be a single device or a distributed
device.
[0020] System 10 may further include various sensors associated
with engine 12 and exhaust system 16 that provide outputs to
controller 50 that are processed by controller 50 to control
operations to reduce NOx output from engine 12 or change the
temperature of the exhaust gas flow 14. As used herein, unless
specified otherwise, a sensor may be a physical sensor that
directly measures an operating condition or output of system 10, or
a virtual sensor in which the operating condition or output is
determined from one or more other sensors and operating parameters.
Not all sensors typically associated with system 10 are shown, and
the illustrated sensors are provided for purposes of illustration
and not limitation.
[0021] System 10 includes at least one sensor 62 that provides an
output to controller 50 to indicate or determine therefrom a NOx
amount at the outlet of vanadia SCR catalyst 22, and at least one
sensor 64 providing an output to controller 50 to indicate a
temperature control operation of system 10 during a temperature
change event for SCR catalyst 22, such as a temperature sensor 64.
Additional sensors may be provided, but are not required, to
measure the exhaust flow, an engine out NOx amount, a temperature
of the exhaust gas flow or exhaust component upstream of vanadia
SCR catalyst 22, sense a condition of engine 12 such as engine
speed or load, measure an NH3 amount at one or more locations along
exhaust system 16, such as at a mid-bed location and/or an outlet
of vanadia SCR catalyst 22.
[0022] In one embodiment, the at least one vanadia SCR catalyst 22
is a reduction catalyst that reduces an amount of the NO.sub.x
during nominal operation, at least partially converting NO.sub.x to
N.sub.2 to reduce the emissions of the internal combustion engine
12. In certain embodiments, aftertreatment system 20 includes an
ammonia oxidation (AMOX) catalyst 24 that is provided downstream of
vanadia SCR catalyst 22, either as a separate device or as a
washcoat applied to a downstream side or portion of vanadia SCR
catalyst 22. Embodiments without an AMOX catalyst 24 are also
contemplated.
[0023] The SCR aftertreatment system 20, during nominal operation,
may reduce NO.sub.x emissions in the presence of a reductant such
as ammonia. The ammonia, where present, may be provided by
injection of urea, which converts to ammonia after evaporation and
hydrolysis in the exhaust gas, and/or by injection of ammonia
directly, and/or by other suitable means. Any suitable reductant
storage and injection means are contemplated, including storage of
the reductant in a liquid medium and/or in a solid storage
medium.
[0024] Since exhaust system 16 lacks a particulate filter that
requires regeneration and an upstream oxidation catalyst, the
thermal conditions created during particulate filter regeneration
that cause hydrothermal aging of a vanadia SCR catalyst can be
avoided or minimized. Use of a vanadia SCR catalyst 22 can be
advantageous due to the greater activity for NO removal and
tolerance to sulphur poisoning that is provided. However, vanadia
SCR catalyst 22 is most effective in reducing NOx when a
temperature condition of the SCR catalyst is in an effective
temperature range for removing NOx. In one embodiment, the
effective temperature for efficient NO.sub.x conversion by vanadia
SCR catalyst 22 is a temperature above about 200.degree. C. and up
to about 400.degree. C., although other effective temperature
ranges and lower thresholds are contemplated depending on catalyst
formulation, feed gas composition, and other parameters. As used
herein a low temperature condition is a condition in which the
temperature of vanadia SCR catalyst 22 is less than the effective
temperature threshold, such as about 200.degree. C., of vanadia SCR
catalyst 22.
[0025] The systems and method disclosed herein determine at least
one parameter associated with operation of the system that
indicates a temperature condition of the vanadia SCR catalyst 22
and initiate a temperature change event by controlling engine
fuelling and controlling at least one of wastegate 86, exhaust
throttle 74 and EGR control valve 92 to produce an exhaust gas flow
that provides a temperature condition for vanadia SCR catalyst 22
that moves the temperature condition of vanadia SCR catalyst 22
into or toward its effective temperature range.
[0026] In one embodiment, the temperature change event includes
changing an amount of exhaust gas recirculated to the intake system
70 to change the temperature of the exhaust gas flow to vanadia SCR
catalyst 22 by controlling EGR control valve 92 and/or the amount
of exhaust gas passing through EGR cooler 96. For example, EGR
cooler 96 can be bypassed in response to a temperature change event
indicating a temperature increase of the exhaust gas flow and
vanadia SCR catalyst 22. In another embodiment, the temperature
change event alternatively or additionally includes changing an
amount of exhaust gas passing through at least one of the wastegate
86 of the turbocharger 80, and/or through the exhaust throttle 74
to increase backpressure on engine 12 and pumping work to increase
or decrease combustion temperatures, changing the temperature
exhaust gas flow and therefore the temperature of vanadia SCR
catalyst 22.
[0027] The systems and method disclosed herein determine at least
one parameter associated with operation of the system that
indicates a NOx output from the vanadia SCR catalyst 22 and
initiate a NOx reduction event in response to the NOx output
exceeding a threshold amount by controlling engine fuelling and
controlling at least one of wastegate 86, exhaust throttle 74 and
EGR control valve 92 to reduce an engine out NOx amount that will
reduce the NOx output from vanadia SCR catalyst 22 toward or below
the threshold amount.
[0028] In one embodiment, the NOx reduction event includes closing
at least one of the wastegate 86 and the exhaust throttle 74 to
increase an amount of exhaust gas flow recirculated to the intake
system 70. In another embodiment, the NOx reduction event
alternatively or additionally includes at least partially closing
each of the wastegate 86 and the exhaust throttle 74 to increase an
amount of exhaust gas flow recirculated to the intake system 70. In
a further embodiment, the NOx reduction event includes opening the
EGR control valve 92 to increase an amount of recirculated exhaust
gas to the intake system 70. In another embodiment, when the
wastegate 86 is open, the NOx reduction event includes closing the
exhaust throttle 74 to provide a minimum exhaust flow and increase
the EGR flow to reduce the NOx output from the engine 12. The
exhaust throttle 74 provides an additional control lever that is
operable independently of the wastegate 86 to control EGR flow to
manage NOx output and/or temperature conditions of the vanadia SCR
catalyst 22.
[0029] The schematic flow diagram in FIG. 3 and related description
which follows provides an illustrative embodiment of performing
procedures for reducing NOx output from engine 12 and a temperature
change event to control operations of system 10 to meet desired NOx
emissions amounts. Operations illustrated are understood to be
exemplary only, and operations may be combined or divided, and
added or removed, as well as re-ordered in whole or part, unless
stated explicitly to the contrary herein. Certain operations
illustrated may be implemented by a computer, such as controller
50, executing a computer program product on a computer readable
medium, where the computer program product comprises instructions
causing the computer to execute one or more of the operations, or
to issue commands to other devices to execute one or more of the
operations.
[0030] Procedure 200 includes an operation 202 that includes
operating the internal combustion engine 12 to procedure exhaust
gas flow 14. Procedure 200 continues at operation 204 that includes
passing the exhaust gas flow 14 through at least one of the turbine
82 and wastegate 86, then exhaust throttle 74, and then vanadia SCR
catalyst 22. During operation 204, controller 50 receives signals
indicative of a NOx output from vanadia SCR catalyst 22 and a
temperature condition of vanadia SCR catalyst 22. In addition,
controller 50 controls operations of reductant injector 30 to
inject reductant into the exhaust gas flow 14 to reduce NOx over
vanadia SCR catalyst 22. The determination of the reductant
injection amount and timing of the injection can be accomplished
with any suitable NOx reduction control scheme.
[0031] Procedure 300 continues at conditional 206 to determine if
the temperature of vanadia SCR catalyst 22 is in its effective
temperature range. If conditional 206 is negative, procedure 300
continues at operation 208 to initiate a temperature change event,
as discussed above. With a temperature change event that involves
the exhaust throttle 74 closed, fuelling of engine 12 from fuel
source 40 can be conducted with a set of fuelling tables that are
based on a closed exhaust throttle to provide fuel pressure, fuel
amounts, start of injection, and injection timing in response to
the load request to engine 12 and to increase a thermal output of
engine 12, resulting in exhaust gas temperatures that are increased
to provide a temperature condition for SCR catalyst 22 that is in
the effective temperature range.
[0032] After completion of operation 208, or if conditional 206 is
positive, procedure 200 then continues at conditional 210 to
determine if the NOx output from vanadia SCR catalyst 22 is greater
than a threshold amount. If conditional 210 is negative, procedure
200 returns to operation 204 and continues until operation of
engine 12 is terminated. If conditional 210 is negative, procedure
200 continues at operation 212 to initiate a NOx reduction event to
reduce NOx output from engine 12, as discussed above, by
controlling one or more of EGR control valve 92, wastegate 86, and
exhaust throttle 74.
[0033] Certain operations described herein include operations to
interpret or determine one or more parameters. Interpreting and/or
determining, as utilized herein, includes receiving values by any
method known in the art, including at least receiving values from a
datalink or network communication, receiving an electronic signal
(e.g. a voltage, frequency, current, or PWM signal) indicative of
the value, receiving a software parameter indicative of the value,
reading the value from a memory location on a computer readable
medium, receiving the value as a run-time parameter by any means
known in the art, and/or by receiving a value by which the
interpreted parameter can be calculated, and/or by referencing a
default value that is interpreted to be the parameter value.
[0034] As is evident from the figures and text presented above, a
variety of aspects, embodiments and refinements of the present
disclosure are contemplated. According to one aspect, a method
includes operating a system including an internal combustion engine
to produce an exhaust gas flow to an exhaust system with a number
of exhaust gas treatment and flow control components consisting
essentially of a vanadia SCR catalyst, an exhaust throttle upstream
of the vanadia SCR catalyst, a turbocharger with a controllable
wastegate upstream of the vanadia SCR catalyst, and an EGR control
valve connected with an EGR conduit connecting the exhaust system
to an intake system to control recirculation of exhaust gas to the
intake system. The method further includes reducing NOx in the
exhaust gas flow with the vanadia SCR catalyst by injecting a
reductant upstream of the vanadia SCR catalyst. The exhaust gas
flow to the passes from the exhaust throttle directly to the
vanadia SCR catalyst without an intervening particulate filter or
oxidation catalyst between the exhaust throttle and the vanadia SCR
catalyst.
[0035] In one embodiment, the method includes determining at least
one parameter associated with operation of the system that
indicates a NOx output level from the vanadia SCR catalyst. The NOx
output event is caused at least in part by operating conditions of
the vanadia SCR catalyst. In response to the NOx output event, the
method includes initiating a NOx reduction event to reduce an
amount of NOx to the vanadia SCR catalyst by reducing a NOx output
by the internal combustion engine.
[0036] In a refinement of this embodiment, reducing the NOx output
includes closing at least one of the wastegate and the exhaust
throttle to increase an amount of exhaust gas flow recirculated to
the intake system. In another refinement, reducing the NOx output
includes at least partially closing each of the wastegate and the
exhaust throttle to increase an amount of exhaust gas flow
recirculated to the intake system. In yet another refinement,
reducing the NOx output includes opening the EGR control valve to
increase an amount of recirculated exhaust gas to the intake
system.
[0037] In another embodiment, the method includes determining at
least one parameter associated with operation of the system that
indicates a temperature condition of the vanadia SCR catalyst and,
in response to the temperature condition falling outside an
effective temperature range, initiating a temperature change event
to change a temperature of the vanadia SCR catalyst. In one
refinement of this embodiment, the temperature change event
includes changing an amount of exhaust gas recirculated to the
intake system. In another refinement, the temperature change event
indicates a temperature increase of the vanadia SCR catalyst and
the method includes bypassing an EGR cooler connected to the EGR
conduit to increase a temperature of the exhaust gas flow. In a
further refinement, the temperature change event includes changing
an amount of exhaust gas passing through at least one of the
wastegate of the turbocharger and the exhaust throttle to change
the temperature of the vanadia SCR catalyst.
[0038] In yet another refinement, the temperature change event
includes changing an amount of exhaust gas passing through the
exhaust throttle to change the temperature of the vanadia SCR
catalyst. In yet another refinement, the temperature change event
includes increasing a temperature condition of the vanadia SCR
catalyst to the effective operating temperature range.
[0039] According to another aspect, a method includes operating a
system including an internal combustion engine to produce an
exhaust gas flow through an aftertreatment system including at
least one vanadia SCR catalyst and a reductant injector upstream of
the vanadia SCR catalyst. The aftertreatment is configured without
a particulate filter and without an oxidation catalyst upstream of
the vanadia SCR catalyst. The method includes determining a NOx
output in the exhaust gas flow from the vanadia SCR catalyst and,
in response to the NOx output being greater than a NOx output
threshold, initiating a NOx output reduction event to reduce a NOx
output by the internal combustion engine. The NOx output reduction
event includes increasing an amount of recirculated exhaust gas by
at least one operation including closing an exhaust throttle
upstream of the vanadia SCR catalyst, closing a wastegate of a
turbocharger upstream of the vanadia SCR catalyst, and opening an
EGR control valve in an EGR system operable to provide exhaust gas
flow to an intake of the internal combustion engine.
[0040] In one embodiment, the at least one operation includes
closing the wastegate of the turbocharger and opening the EGR
control valve. In another embodiment, the at least one operation
includes closing the exhaust throttle and opening the EGR valve
while the wastegate of the turbocharger is open. In yet another
embodiment, the exhaust gas flow passes, in order, through at least
one of the wastegate and the turbocharger, the exhaust throttle and
the vanadia SCR catalyst.
[0041] According to yet another aspect, a system includes an
internal combustion engine operable to receive an intake flow from
an intake system and produce an exhaust gas flow to an exhaust
system. The system also includes a turbocharger including a turbine
in the exhaust system and a compressor in the intake system. The
exhaust system includes an aftertreatment system with a vanadia SCR
catalyst and a reductant injector connected to a reductant source
upstream of the vanadia SCR catalyst. The exhaust system also
includes an exhaust throttle upstream of the vanadia SCR catalyst
and a wastegate associated with the turbine upstream of the exhaust
throttle. The exhaust throttle receives exhaust gas flow from the
turbine and the wastegate and the vanadia SCR catalyst receives
exhaust flow from the exhaust throttle without an intervening
particulate filter and without an intervening oxidation catalyst.
The system further includes an EGR system connecting the exhaust
system to the intake system, and the EGR system includes an EGR
cooler to cool recirculated exhaust gas flow and an EGR control
valve operable to control an amount of recirculated exhaust
gas.
[0042] In one embodiment, the EGR system includes an EGR bypass
around the EGR cooler. In a refinement of this embodiment, the EGR
control valve is upstream of the EGR cooler. In another refinement,
the EGR control valve is downstream of the EGR cooler.
[0043] In another embodiment, the wastegate is an external
wastegate. In a further embodiment, the engine is a diesel engine.
In yet another embodiment, the EGR system is connected to the
exhaust system upstream of the turbine.
[0044] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only certain exemplary embodiments have been
shown and described. Those skilled in the art will appreciate that
many modifications are possible in the example embodiments without
materially departing from this invention. Accordingly, all such
modifications are intended to be included within the scope of this
disclosure as defined in the following claims.
[0045] 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.
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