U.S. patent application number 12/028870 was filed with the patent office on 2009-08-13 for methods to protect selective catalyst reducer aftertreatment devices during uncontrolled diesel particulate filter regeneration.
This patent application is currently assigned to Detroit Diesel Corporation. Invention is credited to Matthew T. Baird, Kevin D. Sisken.
Application Number | 20090199537 12/028870 |
Document ID | / |
Family ID | 40847449 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090199537 |
Kind Code |
A1 |
Sisken; Kevin D. ; et
al. |
August 13, 2009 |
METHODS TO PROTECT SELECTIVE CATALYST REDUCER AFTERTREATMENT
DEVICES DURING UNCONTROLLED DIESEL PARTICULATE FILTER
REGENERATION
Abstract
The present invention is directed to a method to operate an
electronically controlled internal combustion engine with an
exhaust system equipped with a diesel particulate filter upstream
of a selective catalyst reducer to protect the selective catalyst
reducer from premature aging and failure caused by exhaust
temperature heat generated during uncontrolled regeneration of the
diesel particulate filter.
Inventors: |
Sisken; Kevin D.; (Saline,
MI) ; Baird; Matthew T.; (Canton, MI) |
Correspondence
Address: |
RADER, FISHMAN & GRAUER PLLC
39533 WOODWARD AVENUE, SUITE 140
BLOOMFIELD HILLS
MI
48304-0610
US
|
Assignee: |
Detroit Diesel Corporation
Detroit
MI
|
Family ID: |
40847449 |
Appl. No.: |
12/028870 |
Filed: |
February 11, 2008 |
Current U.S.
Class: |
60/273 ; 60/286;
60/295 |
Current CPC
Class: |
F01N 3/106 20130101;
F01N 2610/02 20130101; F02D 41/08 20130101; F01N 3/208 20130101;
F01N 13/009 20140601; F01N 3/2053 20130101; Y02T 10/12 20130101;
Y02T 10/24 20130101; F01N 2410/02 20130101; F01N 3/035 20130101;
F01N 2900/1602 20130101; F01N 2560/06 20130101 |
Class at
Publication: |
60/273 ; 60/295;
60/286 |
International
Class: |
F01N 3/023 20060101
F01N003/023; F01N 3/035 20060101 F01N003/035 |
Claims
1. A method to operate an electronically controlled internal
combustion engine equipped with a Engine Control System (ECS) and
an exhaust system with a Diesel Particulate Filter (DPF) having an
inlet and an outlet, said DPF upstream of a Selective Catalytic
Reducer (SCR) having an inlet and an outlets and at least one
temperature sensor at said SCR inlet or DPF outlet electronically
connected to said ECS to transmit data signals to said ECS
indicative of temperature at said SCR inlet, said SCR in fluid
connection with a urea source; said method to protect the SCR
during uncontrolled DPF regeneration comprising: determining engine
operating mode; determining whether the DPF is regenerating;
sensing whether the SCR inlet temperature exceeds a predetermined
threshold for a predetermined period of time: introducing urea to
said SCR in an amount sufficient to cool the SCR during DPF
regeneration below said predetermined temperature threshold.
2. The method of claim 1, further including a clean up catalyst to
catalyze any excess ammonia slip.
3. The method of claim 1, further including a dump valve responsive
to commands from said ECS to reroute exhaust gas in said exhaust
system to bypass said SCR during uncontrolled DPF regeneration.
4. The method of claim 3 wherein said dump valve is controlled by
said ESC and actuated responsive to the introduction of urea if
said SCR inlet temperature continues to exceed a predetermined
threshold for a predetermined period of time.
5. The method of claim 1, wherein said engine operating mode is
engine idle.
6. The method of claim 1, wherein said urea is introduced to said
SCR by an injector in fluid communication with a urea source; said
injector responsive to commands from said ECS.
7. A method to operate an electronically controlled internal
combustion engine equipped with an Engine Control System (ECS), an
exhaust system equipped with a Diesel Particulate Filter (DPF)
having an inlet and an outlet, said DPF positioned upstream of a
Selective Catalytic Reducer having an inlet and an outlet, at least
one temperature sensor at said SCR inlet electronically connected
to said ECS to transmit data signals to said ECS indicative of
temperature at said SCR inlet, and a protector to prevent
overheating of the SCR during uncontrolled DPF regeneration,
comprising: determining engine operating mode: determining whether
the DPF is regenerating; sensing whether the SCR inlet temperature
exceeds a predetermined threshold for a predetermined period of
time; actuating said protector to prevent overheating of said SCR
during uncontrolled DPF regeneration.
8. The method of claim 7, wherein said protector is comprised of a
source of urea and an injector in fluid communication with said
urea and said SCR to facilitate the introduction of an amount of
urea in sufficient quantity over a sufficient period of time to
cool the SCR inlet below a predetermined temperature for a
predetermined period of time during uncontrolled DPF
regeneration.
9. The method of claim 8, further including a clean tip catalyst to
catalyze any excess ammonia slip.
10. The method of claim 7, wherein said protector is a dump valve
actuated by said ECS to divert exhaust gas from said SCR during
uncontrolled DPF regeneration; said dump valve responsive to
commands from said ESC to divert exhaust from said SCR when said
SCR inlet temperature exceeds a predetermined temperature for a
predetermined period of time during uncontrolled DPF
regeneration.
11. The method of claim 7, wherein the engine operating mode is
engine idle.
12. The method of claim 10, wherein said dump valve vents said
exhaust from said exhaust system.
Description
TECHNICAL FIELD
[0001] On diesel engines requiring both NOx and particulate
aftertreatment systems, it is likely that some systems will use
both urea selective catalytic reducers (SCR) in combination with
diesel particulate filters (DPF). In systems where the DPF is
located upstream of a urea SCR catalyst, any uncontrolled
regenerations or other high temperature excursions in the DPF could
also put the SCR at risk of premature aging and failure. In systems
where the DPF is upstream of the SCR, this is especially a factor.
There is a need to protect the SCR during periods of uncontrolled
DPF regeneration to ensure SCR long service life and prevent
premature aging and failure caused by exposure to high heat.
BRIEF SUMMARY OF THE INVENTION
[0002] In one embodiment, the present invention is directed to a
method to operate an electronically controlled internal combustion
engine equipped with a Engine Control System (ECS) and an exhaust
system with a Diesel Particulate Filter (DPF) having an inlet and
an outlet, the DPF located upstream of a Selective Catalytic
Reducer (SCR) having an inlet and an outlet and at least one
temperature sensor electronically connected to the ECS to transmit
data signals to the ECS indicative of the temperature at the SCR
inlet. The SCR is in fluid connection with a urea source. The
method is directed to protecting the SCR during uncontrolled DPF
regeneration. The method comprises the steps of:
[0003] determining engine operating mode;
[0004] determining whether the DPF is regenerating;
[0005] sensing whether the DPF outlet temperature or SCR inlet
temperature exceeds a predetermined threshold for a predetermined
period of time;
[0006] introducing urea to said SCR in an amount sufficient to
minimize over-temperature to the SCR during DPF regeneration below
said predetermined temperature threshold. In one embodiment, urea
is introduced to the SCR by an injector in fluid communication with
a urea source. The injector is responsive to commands from said
ECS.
[0007] The method may further include a clean up catalyst to
catalyze any excess ammonia slip that may be produced by the
introduction of urea to cool the SCR. The method may further
include the use of a dump valve responsive to commands from the ECS
to reroute some or all of the exhaust gas in said exhaust system to
bypass said SCR during uncontrolled DPF regeneration. The dump
valve is controlled by the ESC and actuated responsive to the
introduction of urea. If, after the introduction of urea, the SCR
inlet temperature continues to exceed a predetermined threshold for
a predetermined period of time the ESC actuates the dump valve to
divert the flow of exhaust gas from the SCR, thereby cooling the
SCR. The diverted exhaust gas may be vented to the atmosphere or
diverted around the SCR and from there, out of the exhaust
system.
[0008] While the method is effective at all modes of engine
operation, preferably, enhanced SCR inlet temperature cooling
results may be seen when the engine operating mode is engine
idle.
[0009] In another embodiment, the present invention is directed to
a method to operate an electronically controlled internal
combustion engine equipped with an Engine Control System (ECS), an
exhaust system equipped with a Diesel Particulate Filter (DPF)
having an inlet and an outlet. At least one temperature sensor is
position proximal to the SCR inlet and is electronically connected
to the ECS to transmit data signals indicative of the temperature
at the SCR inlet. The DPF is positioned upstream of a Selective
Catalytic Reducer having an inlet and an outlet, and the exhaust
system is further provided with a protector to prevent overheating
of the SCR during uncontrolled DPF regeneration. The method
comprises the steps of:
[0010] determining engine operating mode:
[0011] determining whether the DPF is regenerating;
[0012] sensing whether the DPF outlet temperature or SCR inlet
temperature exceeds a predetermined threshold for a predetermined
period of time;
[0013] actuating the protector to prevent overheating of the SCR
during uncontrolled DPF regeneration.
[0014] In one embodiment, the protector may be comprised of a
source of urea and an injector in fluid communication with said
urea and said SCR to facilitate the introduction of an amount of
urea in sufficient quantity over a sufficient period of time to
cool the SCR inlet below a predetermined temperature for a
predetermined period of time during uncontrolled DPF regeneration.
A clean up catalyst is used to catalyze any excess ammonia slip
from the introduction of urea to the SCR during DPF
regeneration.
[0015] In another embodiment, the protector may be a dump valve
actuated by said ECS to divert some or all of the exhaust gas from
the SCR during uncontrolled DPF regeneration. The dump valve is
responsive to commands from the ECS to divert exhaust from the SCR
when the SCR inlet temperature exceeds a predetermined temperature
for a predetermined period of time during uncontrolled DPF
regeneration.
[0016] Whereas the methods of the present invention are useful and
operational at all modes of engine operation, enhanced results are
seen when the engine is operating at engine idle mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic representation of an engine system
showing the various systems and components, including an exhaust
system with a DPF upstream of an SCR.
[0018] FIG. 2 is a software flow chart of one embodiment according
to the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0019] Turning now to the drawings wherein like numbers refer to
like structures, vehicle system 10 includes internal combustion
engine 12 having cylinders 14 disposed within block 16 for
reciprocal movement therein. The engine may be of any construction,
such as a spark ignition engine or a compression ignition engine,
and is preferably a compression ignition type engine. The engine is
electronically controlled by an Engine Control System 18 (ECS) that
may be comprised of a single module or multiple modules, as is well
known in the art. The ECS has memory, such as PROM, EPROM, EEPROM,
FLASH, volatile and nonvolatile memory, and may also have tables or
maps therein within which are loaded operating instructions and
other information necessary for the operation and control of the
engine and any system. In a preferred embodiment, the Engine
Control System has DDEC operating instructions and programs loaded
therein such as is available from Detroit Diesel Corporation. The
ECS communicates and controls the engine through the engine
communication area network (ECAN) 20 that permits the ECS to
receive sensor input from the engine and to send commands from the
ECS to control operation of the engine.
[0020] The engine has an exhaust system 22 comprised of an exhaust
conduit 24 in fluid communication with an exhaust 21 of the engine
to vent exhaust gasses 62 out of exhaust exit 60 that are produced
in the combustion chambers of the engine to the ambient atmosphere
after it is treated for removal of Particulate Matter (PM), and
NOx. The exhaust system is preferably equipped with a Diesel
Particulate Filter (DPF) 26 to remove PM from the exhaust gasses.
The DPF has an inlet 28 and an outlet 30. In close proximity to the
DPF outlet, a pressure sensor 32 is disposed to send data signals
indicative of DPF inlet pressure to the ECS. The ECS determines if
the DPF inlet pressure is indicative of a clogged DPF filter, at
which time, it initiates a regeneration of the DPF by controlling
fueling, timing, BOT, engine mode of operation, engine load and
engine speed, etc., of the engine to create the requisite heat in
the exhaust stream to burn the PM and other hydrocarbon
contaminates from the DPF filter. Generally, the DPF is upstream
from a Selective Catalyst Reducer 42. The SCR has an inlet 44 and
an outlet 50. At least one temperature sensor 46 is disposed
proximal to said SCR inlet and is in electronic communication 48
with the ECS to transmit data signals to the ECS indicative of the
temperature of the exhaust gasses at the SCR inlet. Disposed in
conduit 24 intermediate to the DPF and the SCR is a dump or
diverter valve 36 that is actuated by the ECS over electronic
communication 38 in response to temperature readings received from
the temperature sensor 46. Valve 36 may be actuated to divert the
flow of exhaust gasses around the SCR when it is determined that
the temperature at the SCR inlet exceeds a predetermined threshold
for a predetermined period of time. In one embodiment, when the
exhaust temperature exceeds that threshold of temperature and time,
the ECS actuates the valve to divert the flow of exhaust gas
through diverter conduit 40 around the SCR and exits the exhaust
gas to the ambient atmosphere through exhaust exit 60. The exhaust
system may further be equipped with a urea injector 56 that is
electronically controlled by the ECS responsive to the temperature
at the SCR inlet. When the temperature inlet temperature exceeds a
predetermined threshold for a predetermined period of time, the ECS
causes the urea injector to inject urea from urea source 52 through
urea conduit 54 to the SCR inlet in an attempt to cool the SCR
temperature. The amount of urea to be injected during the methods
of the present invention is dependent upon the temperature at the
SCR inlet, and is in an amount sufficient to cool the SCR inlet
temperature below a predetermined threshold for predetermined
period of time. In order to accommodate the injection of urea into
the exhaust stream, a catalytic cleaner 64 may be utilized in the
exhaust conduit downstream of the SCR to effectively neutralize any
ammonia slip caused by the introduction of excessive urea into the
SCR during DPF regeneration events.
[0021] FIG. 2 is a software flowchart showing one embodiment of one
method 66 of the present invention. Specifically, step 68 is
determining the engine mode of operation. Step 70 is determining
whether the DPF is regenerating. Generally, DPF regeneration occurs
during idle engine operation as well as during on highway engine
operation. A runaway DPF regeneration event usually occurs during a
drop to idle engine mode of operation, and is of particular concern
as such an event generates a great amount of heat in the exhaust
gas stream. The excessive exhaust heat, especially that generated
during a runaway DPF regeneration event may harm the SCR or, in the
very least, may contribute to premature aging and failure of the
SCR. Step 72 is sensing the temperature at the SCR inlet. If the
temperate at the SCR inlet exceeds a predetermined temperature for
a predetermined period of time, step 74 is actuating a protector to
control the temperature of the SCR. In one embodiment, this step
includes injecting urea in an amount sufficient to cool the SCR
below the predetermined temperature threshold for a predetermined
period of time. In the event the injection of urea does not cool
the SCR sufficiently, a protector such as the diverter valve may be
actuated to divert the flow of hot exhaust gas from the SCR. In
another embodiment, the dump valve is actuated to divert the flow
off exhaust gas through the exhaust conduit around the SCR to help
cool the SCR.
[0022] The words used in the specification are understood to be
words of description, and not words of limitation. Many variations
and modifications are possible without departing form the scope and
spirit of the invention as set forth in the appended claims.
* * * * *