U.S. patent application number 10/931017 was filed with the patent office on 2005-07-14 for method and apparatus for operating an airless fuel-fired burner of an emission abatement assembly.
Invention is credited to Berkman, Mert E., Crane, Samuel N. JR., Huckaby, Jon J., Kong, Yougen, Taylor, William III.
Application Number | 20050150215 10/931017 |
Document ID | / |
Family ID | 34743716 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050150215 |
Kind Code |
A1 |
Taylor, William III ; et
al. |
July 14, 2005 |
Method and apparatus for operating an airless fuel-fired burner of
an emission abatement assembly
Abstract
A method of operating an emission abatement assembly to remove
soot from the exhaust gas of an internal combustion engine includes
determining if the engine is operating with predetermined operating
conditions and regenerating a particulate filter if the engine is
within such conditions. An emission abatement assembly is also
disclosed.
Inventors: |
Taylor, William III;
(Columbus, IN) ; Kong, Yougen; (Greenwood, IN)
; Berkman, Mert E.; (Greenwood, SC) ; Huckaby, Jon
J.; (Westport, IN) ; Crane, Samuel N. JR.;
(Columbus, IN) |
Correspondence
Address: |
BARNES & THORNBURG
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
|
Family ID: |
34743716 |
Appl. No.: |
10/931017 |
Filed: |
August 31, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60536327 |
Jan 13, 2004 |
|
|
|
60546139 |
Feb 20, 2004 |
|
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|
Current U.S.
Class: |
60/295 ;
60/297 |
Current CPC
Class: |
F01N 3/36 20130101; F01N
2330/10 20130101; F01N 2330/12 20130101; F01N 3/025 20130101; F01N
2510/065 20130101; F01N 13/011 20140603; F01N 3/303 20130101; F01N
9/002 20130101; F01N 2240/20 20130101; F01N 13/009 20140601; F01N
2330/06 20130101; F01N 3/023 20130101; Y02T 10/47 20130101; Y02T
10/40 20130101; F01N 3/30 20130101; F01N 3/2892 20130101; F01N
2240/14 20130101; F01N 3/323 20130101; F01N 3/0256 20130101 |
Class at
Publication: |
060/295 ;
060/297 |
International
Class: |
F23N 005/26; F01N
003/00 |
Claims
1. A method of operating an emission abatement assembly to remove
soot from the exhaust gas of an internal combustion engine, the
method comprising the steps of: determining if the engine is
operating within predetermined operating conditions, and operating
a fuel-fired burner to regenerate a particulate filter if the
engine is operating within the predetermined operating
conditions.
2. The method of claim 1, wherein: the determining step comprises
determining if engine speed of the engine is within a predetermined
range, and the operating step comprises operating the fuel-fired
burner to regenerate the particulate filter if the engine speed of
the engine is within the predetermined range.
3. The method of claim 2, wherein determining if the engine speed
of the engine is within a predetermined range comprises monitoring
output from an engine speed sensor.
4. The method of claim 1, wherein: the determining step comprises
determining if engine load of the engine is within a predetermined
range, and the operating step comprises operating the fuel-fired
burner to regenerate the particulate filter if the engine load of
the engine is within the predetermined range.
5. The method of claim 4, wherein determining if engine load of the
engine is within the predetermined range comprises querying an
engine load map.
6. The method of claim 1, wherein: the determining step comprises
determining if an exhaust mass flow from the engine is within a
predetermined range, and the operating step comprises operating the
fuel-fired burner to regenerate the particulate filter if the
exhaust mass flow from the engine is within the predetermined
range.
7. The method of claim 6, wherein determining if an exhaust mass
flow from the engine is within the predetermined range comprises
monitoring output from a mass flow sensor.
8. The method of claim 6, wherein determining if an exhaust mass
flow from the engine is within the predetermined range comprises
estimating the exhaust mass flow from sensed engine operation
parameters.
9. The method of claim 1, wherein the operating step comprises
operating the fuel-fired burner without assistance from a
supplemental air supply.
10. An emission abatement assembly for removing soot from the
exhaust gas of an internal combustion engine, the assembly
comprising: a particulate filter, a fuel-fired burner positioned
upstream of the particulate filter, and a controller configured to
control the fuel-fired burner, the controller comprising (i) a
processor, and (ii) a memory device electrically coupled to the
processor, the memory device having stored therein a plurality of
instructions which, when executed by the processor, cause the
processor to: determine if the engine is operating within
predetermined operating conditions, and operate the fuel-fired
burner to regenerate the particulate filter if the engine is
operating within the predetermined operating conditions.
11. The emission abatement assembly of claim 10, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to: determine if engine speed of the engine is
within a predetermined range, and operating the fuel-fired burner
to regenerate the particulate filter if the engine speed of the
engine is within the predetermined range.
12. The emission abatement assembly of claim 11, further comprising
an engine speed sensor, wherein the plurality of instructions, when
executed by the processor, further cause the processor to monitor
output from the engine speed sensor to determine if the engine
speed of the engine is within the predetermined range.
13. The emission abatement assembly of claim 10, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to: determine if engine load of the engine is
within a predetermined range, and operate the fuel-fired burner to
regenerate the particulate filter if the engine load of the engine
is within the predetermined range.
14. The emission abatement assembly of claim 10, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to query an engine load map to determine if
engine load of the engine is within the predetermined range.
15. The emission abatement assembly of claim 10, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to: determine if an exhaust mass flow from the
engine is within a predetermined range, and operate the fuel-fired
burner to regenerate the particulate filter if the exhaust mass
flow from the engine is within the predetermined range.
16. The emission abatement assembly of claim 15, further comprising
a mass flow sensor, wherein the plurality of instructions, when
executed by the processor, further cause the processor to monitor
output from the mass flow sensor to determine if the exhaust mass
flow from the engine is within the predetermined range.
17. The emission abatement assembly of claim 15, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to estimate the exhaust mass flow from sensed
engine operation parameters.
Description
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Patent Application Ser. No. 60/536,327,
filed on Jan. 13, 2004 and U.S. Provisional Patent Application Ser.
No. 60/546,139 filed on Feb. 20, 2004, the entirety of both of
which is hereby incorporated by reference.
CROSS REFERENCE
[0002] Cross reference is made to copending U.S. patent application
Ser. No. ______ entitled "Method and Apparatus for Cooling the
Components of a Control Unit of an Emission Abatement Assembly" by
Wilbur H. Crawley and Randall J. Johnson (Attorney Docket No.
9501-74001, 04ARM0027); Ser. No. ______ entitled "Method and
Apparatus for Monitoring Engine Performance as a Function of Soot
Accumulation in a Filter" by Randall J. Johnson and Wilbur H.
Crawley (Attorney Docket No. 9501-74002, 04ARM0028); Ser. No.
______ entitled "Method and Apparatus for Shutting Down a
Fuel-Fired Burner of an Emission Abatement Assembly" by Wilbur H.
Crawley and Randall J. Johnson (Attorney Docket No. 9501-74003,
04ARM0033); Ser. No. ______ entitled "Method and Apparatus for
Controlling the Temperature of a Fuel-Fired Burner of an Emission
Abatement Assembly" by Wilbur H. Crawley, Randall J. Johnson, and
Samuel N. Crane, Jr. (Attorney Docket No. 9501-74004, 04ARM0021);
Ser. No. ______ entitled "Emission Abatement Assembly and Method of
Operating the Same" by Wilbur H. Crawley and Randall J. Johnson
(Attorney Docket No. 9501-74005, 04ARM0026); Ser. No. ______
entitled "Method and Apparatus for Cleaning the Electrodes of a
Fuel-Fired Burner of an Emission Abatement Assembly" by Wilbur H.
Crawley, Randall J. Johnson, Stephen P. Goldschmidt, and Edward C.
Kinnaird (Attorney Docket No. 9501-75879, 04ARM0078); Ser. No.
______ entitled "Method and Apparatus for Operating an Airless
Fuel-Fired Burner of an Emission Abatement Assembly" by William
Taylor, III, Yougen Kong, Mert E. Berkman, Jon J. Huckaby, and
Samuel N. Crane, Jr. (Attorney Docket No. 9501-75880, 04ARM0145);
Ser. No. ______ entitled "Method and Apparatus for Directing
Exhaust Gas Through a Fuel-Fired Burner of an Emission Abatement
Assembly" by Wilbur H. Crawley, Randall J. Johnson, Yougen Kong,
John Abel, Shoja Farr, Nicholas Birkby, and David Pearson (Attorney
Docket No. 9501-75881, 04ARM0258); Ser. No. ______ entitled "Method
and Apparatus for Starting up a Fuel-Fired Burner of an Emission
Abatement Assembly" by Wilbur H. Crawley and Randall J. Johnson
(Attorney Docket No. 9501-75882, 04ARM0035); Ser. No. ______
entitled "Method and Apparatus for Controlling a Fuel-Fired Burner
of an Emission Abatement Assembly" by William Taylor, III, Yougen
Kong, Wilbur H. Crawley, and Randall J. Johnson (Attorney Docket
No. 9501-75883, 04ARM0025); Ser. No. ______ entitled "Method and
Apparatus for Determining Accumulation in a Particulate Filter of
an Emission Abatement Assembly" by Wilbur H. Crawley and Randall J.
Johnson (Attorney Docket No. 9501-75884, 04ARM0034); and Ser. No.
______ entitled "Method and Apparatus for Monitoring the Components
of a Control Unit of an Emission Abatement Assembly" by Wilbur H.
Crawley, Randall J. Johnson, and Navin Khadiya (Attorney Docket No.
9501-75886, 04ARM0022/23), each of which is assigned to the same
assignee as the present application, each of which is filed
concurrently herewith, and each of which is hereby incorporated by
reference.
FIELD OF THE DISCLOSURE
[0003] The present disclosure relates generally to diesel emission
abatement devices.
BACKGROUND
[0004] Untreated internal combustion engine emissions (e.g., diesel
emissions) include various effluents such as NO.sub.x,
hydrocarbons, and carbon monoxide, for example. Moreover, the
untreated emissions from certain types of internal combustion
engines, such as diesel engines, also include particulate
carbon-based matter or "soot". Federal regulations relating to soot
emission standards are becoming more and more rigid thereby
furthering the need for devices and/or methods which remove soot
from engine emissions.
[0005] The amount of soot released by an engine system can be
reduced by the use of an emission abatement device such as a filter
or trap. Such a filter or trap is periodically regenerated in order
to remove the soot therefrom. The filter or trap may be regenerated
by use of a burner or electric heater to burn the soot trapped in
the filter.
SUMMARY
[0006] According to one aspect of the disclosure, an emission
abatement assembly includes a pair of fuel-fired burners. Both of
the fuel-fired burners are under the control of a single control
unit. The fuel-fired burners may be selectively operated by the
control unit to regenerate particulate filters.
[0007] According to another aspect of the disclosure, a method of
monitoring a fuel-fired burner during filter regeneration includes
determining the temperature of the heat being produced by the
burner and adjusting the amount of fuel supplied to the burner
based thereon. A predetermined temperature range may be used with
the amount of fuel supplied to the burner being adjusted if the
temperature is outside of the predetermined temperature range. An
electronic controller configured to control the fuel-fired burner
in such a manner is also disclosed. Temperature measurements may be
obtained by use of a temperature sensor.
[0008] According to another aspect of the disclosure, a control
unit for controlling operation of a fuel-fired burner is disclosed.
The control unit includes a housing having an air inlet which is
open to an interior chamber of the housing. An air pump is
positioned in the interior chamber of the housing and has an air
inlet which is open to the interior chamber of the control unit's
housing. The air pump generates reduced air pressure in the
interior chamber which draws air into the housing and into the
pump's inlet. This flow of air cools an electronic controller along
with other components position in the housing. In one exemplary
embodiment, the air pump draws air from the interior chamber of the
housing and supplies the air to a combustion chamber of the
fuel-fired burner to facilitate operation of the burner. An
associated method of advancing air to a fuel-fired burner is also
disclosed.
[0009] According to another aspect of the disclosure, a method of
operating a fuel-fired burner of an emission abatement assembly is
disclosed. The method includes supplying a reduced amount of fuel
to the fuel-fired burner in response to detection of a burner
shutdown request. Such a reduced fuel supply continues for a
predetermined time period after which fuel is no longer supplied to
the burner. In the exemplary embodiment described herein, the
supply of both combustion air and atomization air, along with spark
generation, continues for a period of time after the fuel is
shutoff. After a period of time, combustion air is no longer
supplied to the burner, but atomization air continues to be
supplied and spark generation is maintained. After a period of
time, the supply of atomization air is shutoff and spark generation
ceases. In the exemplary embodiment described herein, a supply of
cleaning air is substantially continuously supplied to the
fuel-fired burner to reduce, or even prevent, clogging of the
burner's fuel inlet nozzle. An electronic controller configured to
control the components of the emission abatement assembly in such a
manner is also disclosed.
[0010] According to another aspect of the disclosure, a method of
monitoring engine performance as a function of soot accumulation in
a particulate filter includes determining characteristics of soot
accumulation in the filter, analyzing the characteristics, and
generating an error signal if the characteristics are indicative of
predetermined engine performance conditions. In one exemplary
embodiment, the rate in which soot accumulates in the filter may be
monitored. An increase in the rate in which soot accumulates in the
filter (beyond predetermined limits) may be indicative of an engine
condition such as excess oil usage or a stuck/leaking fuel
injector. An electronic controller configured to monitor soot
accumulation in such a manner is also herein disclosed.
[0011] According to another aspect of the disclosure, a smoke
detector is used to detect the presence of fuel particles and/or
smoke in the interior chamber of the control unit. If the presence
of fuel particles and/or smoke is detected, the control unit may be
shutdown thereby potentially avoiding damage to the control unit. A
method of monitoring output from such a smoke detector is also
disclosed.
[0012] According to another aspect of the disclosure, a temperature
sensor is used to monitor the temperature within the interior
chamber of the control unit. If the temperature exceeds a
predetermined upper temperature limit, the control unit may be
shutdown thereby potentially avoiding damage to the control unit. A
method of monitoring output from such a temperature sensor is also
disclosed.
[0013] According to another aspect of the present disclosure, a
fuel pressure sensor is used to monitor fuel pressure in a fuel
return line associated with the control unit's fuel pump. If fuel
pressure in the return line exceeds a predetermined upper pressure
limit, the control unit may be shutdown thereby potentially
avoiding damage to the control unit. A method of monitoring output
from such a fuel pressure sensor is also disclosed.
[0014] According to another aspect of the disclosure, a method of
monitoring ash buildup in a particulate filter includes determining
particulate accumulation in the filters subsequent to filter
regeneration and generating an error signal if particulate
accumulation exceeds a predetermined threshold. The particulate
matter remaining in the filter subsequent to filter regeneration
may be attributable to ash. As such, by monitoring the amount of
particulate matter in the filter relatively soon, if not
immediately, after filter regeneration, a determination may be made
as to when the filter is in need of servicing to remove ash
therefrom. An electronic controller configured to monitor ash
buildup in such a manner is also disclosed.
[0015] According to another aspect of the disclosure, the
electronic controller of the emission abatement assembly is
electrically coupled to an engine control unit of an internal
combustion engine. The electronic controller may be coupled to the
engine control unit via a communications interface such as a
Controller Area Network or "CAN" interface. In such a way,
information may be shared between the electronic controller of the
emission abatement assembly and the engine control unit.
[0016] According to another aspect of the present disclosure, a
method of operating a fuel-fired burner includes monitoring the
temperature at the outlet of a particulate filter during a filter
regeneration cycle and adjusting operation of the fuel-fired burner
if the filter outlet temperature exceeds a predetermined limit. In
one embodiment, the fuel-fired burner is shutdown if the filter
outlet temperature exceeds the predetermined limit. Prior to, or in
lieu of, shutdown of the burner, the amount of fuel supplied to the
fuel-fired burner may be reduced if the filter outlet temperature
exceeds the predetermined limit.
[0017] According to another aspect of the present disclosure, a
method of starting up a fuel-fired burner of an emission abatement
assembly includes lowering the fuel rate being supplied to the
burner once flame ignition is detected. The fuel rate is maintained
at this lower level as the assembly preheats. Once preheated, the
fuel level is ramped up to a predetermined operational fuel
level.
[0018] According to another aspect of the disclosure, the
electrodes of a fuel-fired burner are energized for a predetermined
period of time prior to the introduction of fuel into the burner
thereby removing any soot or other debris deposited on the
electrodes.
[0019] According to another aspect of the disclosure, the operating
conditions of the engine are monitored to facilitate airless filter
regeneration. In one specific implementation, filter regeneration
occurs when engine operating conditions are within a predetermined
range.
[0020] According to another aspect of the disclosure, the exhaust
gas flow entering through the gas inlet port of the fuel-fired
burner is separated into a combustion flow which is advanced
through the combustion chamber, and a bypass flow which bypasses
the combustion chamber.
[0021] According to another aspect of the disclosure, soot loading
in a particulate filter is monitored as a function of exhaust mass
flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a rear elevational view of an on-highway truck
with an emission abatement assembly installed thereon;
[0023] FIG. 2 is a perspective view of one of the soot abatement
assemblies of the emission abatement assembly of FIG. 1;
[0024] FIG. 3 is an elevational view of the end of the soot
abatement assembly as viewed in the direction of the arrows of line
3-3 of FIG. 2;
[0025] FIG. 4 is a cross sectional view of the soot abatement
assembly of FIG. 2 taken along the line 4-4 of FIG. 3, as viewed in
the direction of the arrows;
[0026] FIG. 5 is an enlarged cross sectional view of the fuel-fired
burner of the soot abatement assembly of FIG. 4;
[0027] FIG. 6 is a perspective view of the control unit of the
emission abatement assembly of FIG. 1, note that the cover has been
removed for clarity of description;
[0028] FIG. 7 is a side elevational view of the control unit of
FIG. 6;
[0029] FIG. 8 is a diagrammatic view of the emission abatement
assembly of FIG. 1;
[0030] FIG. 9 is a flowchart of a control routine for monitoring
operation of the fuel-fired burners of the emission abatement
assembly during a filter regeneration cycle;
[0031] FIG. 10 is an exemplary temperature graph which demonstrates
aspects of the control routine of FIG. 9;
[0032] FIG. 11 is a flowchart of a control routine for monitoring
the filter outlet temperature during a filter regeneration
cycle;
[0033] FIG. 12 is a flowchart of a control routine for monitoring
engine performance as a function of soot accumulation in the
particulate filters of the emission abatement assembly of FIG.
1;
[0034] FIG. 13 is an exemplary delta pressure versus time graph
which demonstrates aspects of the control routine of FIG. 12;
[0035] FIG. 14 is a flowchart of a control routine for monitoring
ash buildup in the particulate filters of the emission abatement
assembly of FIG. 1;
[0036] FIG. 15 is a flowchart of a control routine for shutting
down the fuel-fired burners of the emission abatement assembly of
FIG. 1;
[0037] FIG. 16 is an exemplary fuel level versus time graph which
demonstrates aspects of the control routine of FIG. 15;
[0038] FIG. 17 is a flowchart of a control routine for monitoring
fuel pressure in the control unit's fuel return line;
[0039] FIG. 18 is a flowchart of a control routine for monitoring
the output from the control unit's smoke detector;
[0040] FIG. 19 is a flowchart of a control routine for monitoring
the output from the control unit's temperature sensor;
[0041] FIG. 20 is a diagrammatic view of another emission abatement
assembly;
[0042] FIG. 21 is view similar to FIG. 20, but showing the emission
abatement assembly configured with a diesel oxidation catalyst
positioned upstream of the filter substrate;
[0043] FIGS. 22 and 23 are diagrammatic views showing the
fuel-fired burner of the assemblies of FIGS. 20 and 21 in greater
detail;
[0044] FIG. 24 is a perspective view showing a portion of the
combustion chamber of the assemblies of FIGS. 20 and 21 in greater
detail;
[0045] FIG. 25 is an elevation view of the portion of the
combustion chamber of FIG. 24 as viewed in the direction of arrow
25-25 of FIG. 24;
[0046] FIG. 26 is an elevation view of a gas distributor;
[0047] FIG. 27 is a view similar to FIGS. 22 and 23, but showing a
different embodiment of the combustion chamber;
[0048] FIG. 28 is an elevation view of a gas distributor;
[0049] FIG. 29 is a diagrammatic view showing both the engine and
the emission abatement assembly under the control of the engine
control unit of the engine;
[0050] FIG. 30 is a flowchart of a control routine for starting up
the fuel-fired burners of the emission abatement assembly of FIG.
1;
[0051] FIG. 31 is an exemplary fuel level versus time graph which
demonstrates aspects of the control routine of FIG. 30;
[0052] FIG. 32 is a flowchart of a control routine for cleaning the
electrodes of the fuel-fired burner;
[0053] FIG. 33 is a flowchart of a control routine for regenerating
an airless fuel-fired burner;
[0054] FIG. 34 is a flowchart of a control routine for triggering
filter regeneration;
[0055] FIG. 35 is a diagrammatic view of another emission abatement
assembly;
[0056] FIGS. 36-43 are views similar to FIG. 5, but showing the
fuel-fired burner with modification thereto;
[0057] FIG. 44 is a development view of a plate which may be
positioned around the combustion chamber; and
[0058] FIG. 45 is a fragmentary perspective view showing the plate
of FIG. 44 positioned around the combustion chamber.
DETAILED DESCRIPTION OF THE DRAWINGS
[0059] As will herein be described in more detail, an emission
abatement assembly 10 for use with an internal combustion engine,
such as the diesel engine of an on-highway truck 12, includes a
pair of soot abatement assemblies 14, 16 under the control of a
control unit 18. As shown in FIG. 1, each of the soot abatement
assemblies 14, 16 has a fuel-fired burner 20, 22 and a particulate
filter 24, 26, respectively. The fuel-fired burners 20, 22 are
positioned upstream (relative to exhaust gas flow from the engine)
from the respective particulate filters 24, 26. During operation of
the engine, exhaust gas flows through the particulate filters 24,
26 thereby trapping soot in the filters. Treated exhaust gas is
released into the atmosphere through exhaust pipes 28, 30. From
time to time during operation of the engine, the control unit 18
selectively operates the fuel-fired burner 20 to regenerate the
particulate filter 24 and the fuel-fired burner 22 to regenerate
the particulate filter 26.
[0060] Referring now to FIGS. 2-5, the soot abatement assembly 14
is shown in greater detail. It should be appreciated that the soot
abatement assembly 14 is substantially identical to the soot
abatement assembly 16. As such, the discussion relating to the soot
abatement assembly 14 of FIGS. 2-5 is relevant to the soot
abatement assembly 16.
[0061] As shown in FIG. 5, the fuel-fired burner 20 of the soot
abatement assembly 14 includes a housing 32 having a combustion
chamber 34 positioned therein. The housing 32 includes an exhaust
gas inlet port 36. As shown in FIG. 1, the exhaust gas inlet port
36 is secured to a T-shaped exhaust pipe 38 which conducts exhaust
gas from the diesel engine of the truck 12 to both soot abatement
assemblies 14, 16.
[0062] The combustion chamber 34 has a number of gas inlet openings
40 defined therein. Engine exhaust gas is permitted to flow into
the combustion chamber 34 through the inlet openings 40. In such a
way, an ignition flame present inside the combustion chamber 34 is
protected from the full engine exhaust gas flow, while controlled
amounts of engine exhaust gas are permitted to enter the combustion
chamber 34 to provide oxygen to facilitate combustion of the fuel
supplied to the burner 20. Exhaust gas not entering the combustion
chamber 34 is directed through a number of openings 42 defined in a
shroud 44 and out an outlet 46 of the housing 32.
[0063] The fuel-fired burner 20 includes an electrode assembly
having a pair of electrodes 48, 50. As will be discussed in greater
detail herein, the electrodes 48, 50 are electrically coupled to
igniters of the control unit 18. When power is applied to the
electrodes 48, 50, a spark is generated in the gap 52 between the
electrodes 48, 50. Fuel enters the fuel-fired burner 20 through a
fuel inlet nozzle 54 and is advanced through the gap 52 between the
electrodes 48, 50 thereby causing the fuel to be ignited by the
spark generated by the electrodes 48, 50. It should be appreciated
that the fuel entering the nozzle 54 is generally in the form of a
controlled air/fuel mixture.
[0064] The fuel-fired burner 20 also includes a combustion air
inlet 56. As will be discussed in greater detail herein, an air
pump associated with the control unit 18 generates a flow of
pressurized air which is advanced to the combustion air inlet 56
via an air line 58 (see FIG. 1). During regeneration of the
particulate filter 24, a flow of air is introduced into the
fuel-fired burner 20 through the combustion air inlet 56 to provide
oxygen (in addition to oxygen present in the exhaust gas) to
sustain combustion of the fuel.
[0065] As shown in FIGS. 2 and 4, the particulate filter 24 is
positioned downstream from the outlet 46 of the housing 32 of the
fuel-fired burner 20 (relative to exhaust gas flow). The
particulate filter 24 includes a filter substrate 60. As shown in
FIG. 4, the substrate 60 is positioned in a housing 62. The filter
housing 62 is secured to the burner housing 32. As such, gas
exiting the burner housing 32 is directed into the filter housing
62 and through the substrate 60. The particulate filter 24 may be
any type of commercially available particulate filter. For example,
the particulate filter 24 may be embodied as any known exhaust
particulate filter such as a "deep bed" or "wall flow" filter. Deep
bed filters may be embodied as metallic mesh filters, metallic or
ceramic foam filters, ceramic fiber mesh filters, and the like.
Wall flow filters, on the other hand, may be embodied as a
cordierite or silicon carbide ceramic filter with alternating
channels plugged at the front and rear of the filter thereby
forcing the gas advancing therethrough into one channel, through
the walls, and out another channel. Moreover, the filter substrate
60 may be impregnated with a catalytic material such as, for
example, a precious metal catalytic material. The catalytic
material may be, for example, embodied as platinum, rhodium,
palladium, including combinations thereof, along with any other
similar catalytic materials. Use of a catalytic material lowers the
temperature needed to ignite trapped soot particles.
[0066] The filter housing 62 is secured to a housing 64 of a
collector 66. Specifically, an outlet 88 of the filter housing 62
is secured to an inlet 68 of the collector housing 64. As such,
processed (i.e., filtered) exhaust gas exiting the filter substrate
60 (and hence the filter housing 62) is advanced into the collector
66. The processed exhaust gas is then advanced into the exhaust
pipe 28 and hence released to the atmosphere through a gas outlet
70. It should be appreciated that the gas outlet 70 may be coupled
to the inlet (or a pipe coupled to the inlet) of a subsequent
emission abatement device (not shown) if the truck 12 is equipped
with such a device.
[0067] Referring now to FIGS. 6-8, there is shown the control unit
18 in greater detail. The control unit 18 includes a housing 72
which defines an interior chamber 112. Numerous components
associated with the control unit 18 are positioned in the interior
chamber 112 of the housing 72. For ease of description, a sealed
cover 74 (see FIG. 1) has been removed from the housing in FIGS. 6
and 7 to expose the components within the housing 72. The control
unit 18 includes an electronic control unit (ECU) or "electronic
controller" 76. The electronic controller 76 is positioned in the
interior chamber 112 of the housing 72. The electronic controller
76 is, in essence, the master computer responsible for interpreting
electrical signals sent by sensors associated with the emission
abatement assembly 10 (and in some cases, the engine 80) and for
activating electronically-controlled components associated with the
emission abatement assembly 10. For example, the electronic
controller 76 is operable to, amongst many other things, determine
when one of the particulate filters 24, 26 of the soot abatement
assemblies 14, 16 is in need of regeneration, calculate and control
the amount and ratio of air and fuel to be introduced into the
fuel-fired burners 20, 22, determine the temperature in various
locations within the soot abatement assemblies 14, 16, operate
numerous air and fuel valves, and communicate with an engine
control unit 78 associated with the engine 80 of the truck 12.
[0068] To do so, the electronic controller 76 includes a number of
electronic components commonly associated with electronic units
utilized in the control of electromechanical systems. For example,
the electronic controller 76 may include, amongst other components
customarily included in such devices, a processor such as a
microprocessor 82 and a memory device 84 such as a programmable
read-only memory device ("PROM") including erasable PROM's (EPROM's
or EEPROM's). The memory device 84 is provided to store, amongst
other things, instructions in the form of, for example, a software
routine (or routines) which, when executed by the processor 80,
allows the electronic controller 76 to control operation of the
emission abatement assembly 10.
[0069] The electronic controller 76 also includes an analog
interface circuit 86. The analog interface circuit 86 converts the
output signals from the various sensors (e.g., temperature sensors)
into a signal which is suitable for presentation to an input of the
microprocessor 82. In particular, the analog interface circuit 86,
by use of an analog-to-digital (A/D) converter (not shown) or the
like, converts the analog signals generated by the sensors into a
digital signal for use by the microprocessor 82. It should be
appreciated that the A/D converter may be embodied as a discrete
device or number of devices, or may be integrated into the
microprocessor 82. It should also be appreciated that if any one or
more of the sensors associated with the emission abatement assembly
10 generate a digital output signal, the analog interface circuit
86 may be bypassed.
[0070] Similarly, the analog interface circuit 86 converts signals
from the microprocessor 82 into an output signal which is suitable
for presentation to the electrically-controlled components
associated with the emission abatement assembly 10 (e.g., the fuel
injectors, air valves, igniters, pump motor, etcetera). In
particular, the analog interface circuit 86, by use of a
digital-to-analog (D/A) converter (not shown) or the like, converts
the digital signals generated by the microprocessor 82 into analog
signals for use by the electronically-controlled components
associated with the emission abatement assembly 10. It should be
appreciated that, similar to the A/D converter described above, the
D/A converter may be embodied as a discrete device or number of
devices, or may be integrated into the microprocessor 82. It should
also be appreciated that if any one or more of the
electronically-controlled components associated with the emission
abatement assembly 10 operate on a digital input signal, the analog
interface circuit 86 may be bypassed.
[0071] Hence, the electronic controller 76 may be operated to
control operation of the fuel-fired burners 20, 22. In particular,
the electronic controller 76 executes a routine including, amongst
other things, a closed-loop control scheme in which the electronic
controller 76 monitors outputs of the sensors associated with the
emission abatement assembly 10 to control the inputs to the
electronically-controlled components associated therewith. To do
so, the electronic controller 76 communicates with the sensors
associated with the emission abatement assembly to determine,
amongst numerous other things, the temperature at various locations
within the soot abatement assemblies 14, 16 and the pressure drop
across the filter substrate 60. Armed with this data, the
electronic controller 76 performs numerous calculations each
second, including looking up values in preprogrammed tables, in
order to execute algorithms to perform such functions as
determining when or how long the fuel injectors are operated,
controlling the power level input to the electrodes 48, 50,
controlling the air advanced through combustion air inlet 56,
etcetera.
[0072] The control unit 18 also includes an air pump 90. The air
pump 90 is driven by an electric motor 92 which is under the
control of the electronic controller 76. The motor 92 drives a
pulley 94 which in turn drives the air pump 90. A signal line 96
electrically couples the air pump 90 to the electronic controller
76. The outlet 98 of the air pump 90 is coupled to an inlet 100 of
an electronically-controlled air valve 102 via an air line 104. A
first outlet 106 of the air valve 102 is coupled to the combustion
air inlet 56 of the fuel-fired burner 20 via one of the air lines
58, whereas a second outlet 108 of the air valve 102 is combustion
air inlet 56 of the fuel-fired burner 22 via the other air line
58.
[0073] The air valve 102 is electrically coupled to the electronic
controller 76 via a signal line 110. As such, the electronic
controller 76 may control position of the valve 102. In particular,
the electronic controller 76 may position the air valve 102 in
either a first valve position in which combustion air from the air
pump 90 is directed to the fuel-fired burner 20 or a second valve
position in which combustion air from the air pump 90 is directed
to the fuel-fired burner 22. As will herein be described in greater
detail, the controller 76 operates the air valve 102 to direct
combustion air to the fuel-fired burner 20, 22 associated with the
particulate filter 24, 26 undergoing regeneration.
[0074] As shown in FIGS. 6 and 7, the inlet 114 of the air pump 90
is open to the interior chamber 112 of the control housing 72. As
such, the air pump 90 draws air from the interior chamber 112 of
the control housing 72. The control housing 72 has an air inlet
116. The air inlet 116 is open to the interior chamber 112. An air
filter 118 is secured to the housing 72 and is positioned to filter
air being drawn into the interior chamber 112 through the air inlet
116. When operated, the air pump 90 generates reduced air pressure
in the interior chamber 112 thereby drawing air from the atmosphere
through the filter 118, the air inlet 116, and into the interior
chamber 112. Air in the interior chamber 112 is then drawn into the
pump inlet 114 and pumped to the air valve 102. When the cover 74
is secured in place (see FIG. 1), the housing 72 is substantially
sealed such that substantially all of the air drawn into the
interior chamber 112 by the air pump 90 is drawn through the filter
118 (and hence the air inlet 116).
[0075] Since both the pump inlet 114 and the housing inlet 116 are
open to the interior chamber 112 (as opposed to being coupled to
one another, for example, by an air hose or other type of conduit),
a flow of air is generated in the interior chamber 112 as air
advances from the housing inlet 116 to the pump inlet 114. Such an
arrangement facilitates cooling of the electronic controller 76
since the controller 76 is exposed to at least a portion of the air
flow in the interior chamber 112. In particular, the electronic
controller 76 generates heat during operation thereof. Heat from
the electronic controller 76 is transferred to the air advancing
through the interior chamber 112 thereby cooling the electronic
controller 76. Such an arrangement facilitates the placement of the
controller 76 in the housing 72 (as opposed to positioning the
controller outside the housing 72 to be exposed to atmospheric
temperatures). Moreover, in certain embodiments, cooling the
electronic controller 76 in such a manner eliminates the need for
heatsinks or other heat dissipating devices.
[0076] The control unit 18 also includes a fuel delivery assembly
120 configured to supply a desired mixture of air and fuel
("air/fuel mixture") to the fuel-fired burners 20, 22. In
particular, the fuel-fired burners 20, 22 combust or otherwise
process fuel in the form of a mixture of air and fuel. As is
defined in this specification, the term "air/fuel mixture" is
defined to mean a mixture of any amount of air and any amount of
fuel including a "mixture" of only fuel. Moreover, the term
"air-to-fuel ratio" is intended to mean the relationship between
the air component and the fuel component of such air/fuel
mixtures.
[0077] One illustrative embodiment of the fuel delivery assembly
120 will herein be described in greater detail. However, it should
be appreciated that such a description is exemplary in nature and
that the fuel delivery assembly 120 may be embodied in numerous
different configurations.
[0078] In the illustrative embodiment described herein, the fuel
delivery assembly 120 includes a fuel pump 122 which draws diesel
fuel from a fuel tank 124 of the truck 12 via a fuel line 126. A
fuel filter 128 filters the fuel drawn from the tank 124. As shown
in FIGS. 6 and 7, the motor-driven pulley 94 drives an input shaft
130 of the fuel pump 122. As such, the motor 92 drives both the air
pump 90 and the fuel pump 122.
[0079] The fuel pump 122 supplies a pressurized flow of fuel to a
pair of electronically-controlled fuel injectors 132, 134. As shown
in FIG. 8, a signal line 136 electrically couples the fuel injector
132 to the electronic controller 76 thereby allowing the controller
76 to control operation of the injector 132. Similarly, a signal
line 138 electrically couples the fuel injector 134 to the
electronic controller 76 thereby allowing the controller 76 to
control operation of the injector 134.
[0080] An electronically-controlled fuel enable valve 140
selectively allows fuel to be supplied to the fuel injectors 132,
134 from the fuel pump 122. Specifically, when positioned in an
open valve position, the fuel enable valve 140 allows fuel to be
advanced to the fuel injectors 132, 134. However, when the fuel
enable valve 140 is positioned in a closed valve position, fuel is
not supplied to the fuel injectors 132, 134. Fuel pumped by the
pump 122, but not supplied to the injectors 132, 134, is returned
to the truck's fuel tank 124 via a fuel return line 142. The fuel
enable valve 140 is electrically coupled to the electronic
controller 76 via a signal line 144. The electronic controller 76
generates output signals on the signal line 144 to control
operation (e.g., position) of the fuel enable valve 140.
[0081] The fuel injectors 132, 134 are selectively operated by the
electronic controller 76 to inject quantities of fuel into a mixing
chamber 146 where the fuel is mixed with air to produce an air/fuel
mixture having a desired air-to-fuel ratio which is then delivered
to the fuel inlet nozzle 54 of the fuel-fired burners 20, 22 by a
pair of fuel lines 148, 150. Specifically, the electronic
controller 76 generates output signals on the signal line 136 which
cause the fuel injector 132 to inject a specific desired quantity
of fuel into the mixing chamber 146 where the fuel mixes with air
and is delivered to the fuel inlet nozzle 54 of the fuel-fired
burner 20 via the fuel line 148. Similarly, the electronic
controller 76 generates output signals on the signal line 138 which
cause the fuel injector 134 to inject a specific desired quantity
of fuel into the mixing chamber 146 where the fuel mixes with air
and is delivered to the fuel inlet nozzle 54 of the fuel-fired
burner 22 via the fuel line 150.
[0082] In the exemplary embodiment described herein, the air
delivered to the mixing chamber 146 is supplied from a pressurized
air source 150 associated with the truck 12. For example, the
pressurized air source 150 may be the truck's pneumatic brake
pump(s). Pressurized air from the air source 150 is supplied to the
control unit 18 via an air line 152. A pair of
electronically-controlled air valves 154, 156 control the amount of
air supplied to the mixing chamber 146.
[0083] The air valve 154 supplies a flow of cleaning air which, as
described herein in greater detail, is generally constantly
supplied to the mixing chamber 146 during operation of the engine
80 of the truck 12. Such a flow of air prevents the accumulation of
debris (e.g., soot) in the fuel inlet nozzles 54 of the fuel-fired
burners 20, 22. Such a flow of cleaning air may be pulsed at
relatively high pressure for short interval of time to reduce
clogging of the nozzles 54 with soot or other debris. For example,
under software control, the cleaning air flow may be pulsed such
that the air is supplied at, for example, 60 psi for 15 seconds,
and then shutoff (or reduced in pressure) for 45 seconds, and then
pulsed again, and so on. It has been found that such rapid
increases in air pressure create a force or "shock" which
facilitates soot removal.
[0084] As shown in FIG. 8, the air valve 156 is positioned in a
parallel flow arrangement with the cleaning air valve 154. The air
valve 156 supplies a flow of air which is summed with the air flow
from the cleaning air valve 154. This combined flow of air is used
for fuel atomization during operation of the fuel-fired burners 20,
22. As such, during regeneration of one of the particulate filters
24, 26, both the atomization air valve 156 and the cleaning air
valve 154 are positioned in their respective open valve positions
to supply air to the mixing chamber 146 to atomize the fuel
injected into the mixing chamber 146 by the fuel injectors 132,
134.
[0085] The cleaning air valve 154 is electrically coupled to the
electronic controller 76 via a signal line 158. The electronic
controller 76 generates output signals on the signal line 158 to
control operation (e.g., position) of the cleaning air valve 154.
Similarly, the atomization air valve 156 is electrically coupled to
the electronic controller 76 via a signal line 160. The electronic
controller 76 generates output signals on the signal line 160 to
control operation (e.g., position) of the atomization air valve
156.
[0086] As shown in FIG. 8, air exiting the air valves 154, 156 is
supplied to the mixing chamber 146 via an air line 162. A pressure
transducer 164 senses the air pressure in the air line 162. The
output from the transducer 164 is communicated to the electronic
controller 76 via a signal line 166. The output from the transducer
164 may be used by the electronic controller 76 to verify that a
desired air flow is being supplied to the mixing chamber 146. For
example, in the exemplary embodiment described herein, the
air-to-fuel ratio of the air/fuel mixture being supplied to the
fuel-fired burners 20, 22 is varied by varying the amount of fuel
injected into the mixing chamber 146 with the amount of air
supplied to the mixing chamber 146 remaining substantially
constant. As such, the output from the pressure transducer 164 may
be monitored by the electronic controller 76 to confirm that the
desired, substantially constant flow of air is being supplied to
the mixing chamber 146.
[0087] As described above, fueling of the fuel-fired burners 20, 22
is adjusted by altering the amount of fuel added to a substantially
constant flow of atomization air. For example, to increase the
amount of fuel being supplied to the fuel-fired burner 20 (i.e., to
decrease the air-to-fuel ratio of the air/fuel mixture being
supplied to the burner 20), the electronic controller 76 operates
the fuel injector 132 to increase the amount of fuel being injected
into the mixing chamber 146 with the amount of air being introduced
into the mixing chamber 146 remaining substantially constant.
Similarly, to increase the amount of fuel being supplied to the
fuel-fired burner 22 (i.e., to decrease the air-to-fuel ratio of
the air/fuel mixture being supplied to the burner 20), the
electronic controller 76 operates the fuel injector 134 to increase
the amount of fuel being injected into the mixing chamber 146 with
the amount of air being introduced into the mixing chamber 146
remaining substantially constant.
[0088] Conversely, to decrease the amount of fuel being supplied to
the fuel-fired burner 20 (i.e., to increase the air-to-fuel ratio
of the air/fuel mixture being supplied to the burner 20), the
electronic controller 76 operates the fuel injector 132 to decrease
the amount of fuel being injected into the mixing chamber 146 with
the amount of air being introduced into the mixing chamber 146
remaining substantially constant. To decrease the amount of fuel
being supplied to the fuel-fired burner 22 (i.e., to increase the
air-to-fuel ratio of the air/fuel mixture being supplied to the
burner 20), the electronic controller 76 operates the fuel injector
134 to decrease the amount of fuel being injected into the mixing
chamber 146 with the amount of air being introduced into the mixing
chamber 146 remaining substantially constant.
[0089] As shown in FIG. 8, a pressure regulator 168 regulates the
fluid pressure in the mixing chamber 146. Specifically, the
pressure regulator 168 ensures that a predetermined pressure is not
exceeded in the mixing chamber 146. For example, in many commercial
systems, air from the truck's pressurized air source 150 is present
at 90 psi. The pressure regulator 168 reduces the pressure of the
air delivered to the mixing chamber 146 to a lower level such as,
for example, 40 psi.
[0090] The control unit 18 also includes a pair of ignition devices
or igniters 170, 172. The igniters 170, 172 are electrically
coupled to the electronic controller 76 via signal lines 174, 176,
respectively. As such, the controller 76 may selectively generate
control signals on the signal lines 174, 176 to control operation
of the igniters 170, 172. The igniter 170 is electrically coupled
to the electrodes 48, 50 of the fuel-fired burner 20 via a high
voltage cable 178, whereas igniter 172 is electrically coupled to
the electrodes 48, 50 of the fuel-fired burner 22 via a high
voltage cable 180. Actuation of the igniter 170 causes a spark to
be generated in the gap 52 between the electrodes 48, 50 of the
fuel-fired burner 20 thereby igniting the air/fuel mixture entering
the burner 20 through the fuel inlet nozzle 54. Similarly,
actuation of the igniter 172 causes a spark to be generated in the
gap 52 between the electrodes 48, 50 of the fuel-fired burner 22
thereby igniting the air/fuel mixture entering the burner 22
through the fuel inlet nozzle 54.
[0091] The igniters 170, 172 may be embodied as any type of device
suitable to generate the spark across the electrode gap 52 of the
electrodes 48, 50. For example, the igniters 170, 172 may be
embodied as one or more of the devices disclosed in U.S. patent
application Ser. No. 10/737,333 (Attorney Docket No. 9501-73714,
ArvinMeritor Docket No. 03MRA0454) entitled "Power Supply and
Transformer" which was filed on Dec. 16, 2003 by Stephen P.
Goldschmidt and Wilbur H. Crawley. The entirety of this patent
application is hereby incorporated by reference.
[0092] As alluded to above, the electronic controller 76 monitors
the output of a number of sensors associated with the soot
abatement assemblies 14, 16. For example, each of the soot
abatement assemblies 14, 16 includes a flame temperature sensor
182, a control temperature sensor 184, and a outlet temperature
sensor 186. The temperature sensors 182, 184, 186 are electrically
coupled to the electronic controller 76 via signal lines 188, 190,
192, respectively. As shown in FIGS. 2-5, the temperature sensors
182, 184, 186 may be embodied as thermocouples which extend through
the housings of the soot abatement assemblies 14, 16, although
other types of sensors may also be used.
[0093] The electronic controller 76 monitors output from the flame
temperature sensor 182 to detect or otherwise determine presence of
an ignition flame in the combustion chamber 34 of the fuel-fired
burner 20, 22. Specifically, when the electronic controller 76
initiates ignition of the fuel-fired burner 20, 22, the controller
76 may monitor output from the flame temperature sensor 182 to
ensure that the air/fuel mixture entering the burner 20, 22 is
being ignited by the spark from the electrodes 48, 50. An error
signal is generated if the output of the flame temperature sensor
does not meet a predetermined criteria.
[0094] The electronic controller 76 monitors output from the
control temperature sensor to adjust the fueling of the fuel-fired
burner 20, 22 to maintain the temperature of the heat exerted the
particulate filter 24, 26 within a predetermined temperature range.
For example, a temperature control range may be designed that
allows for sufficient heat to adequately regenerate the particulate
filter 24, 26, while also preventing the filter 24, 26 from being
exposed to excessive temperatures that may damage the filter 24,
26. It should be appreciated that a temperature control range may
be designed to meet many other objectives.
[0095] An exemplary temperature control routine 200 for controlling
the fuel-fired burners 20, 22 during filter regeneration is shown
in FIGS. 9 and 10. The control routine 200 begins with step 202 in
which the electronic controller 76 determines the temperature of
the heat generated by the burner. In particular, the electronic
controller 76 scans or otherwise reads the signal line 190 to
monitor output from the control temperature sensor 184. Once the
electronic controller 76 has determined the temperature of the heat
being generated by the fuel-fired burner 20, 22, the routine 200
advances to step 204.
[0096] In step 204, the electronic controller 76 determines if the
sensed temperature of the heat generated by the fuel-fired burner
20, 22 is within a predetermined temperature control range. In
particular, as described herein, a predetermined temperature
control range may be established. In the exemplary embodiment
described herein, a target temperature (e.g., 650.degree. C. if the
particulate filter 24, 26 is non-catalyzed or 350.degree. C. if the
filter 24, 26 is catalyzed) may be utilized in conjunction with a
predetermined upper and lower control limit (see FIG. 10). As such,
in step 204, the electronic controller 76 determines if the sensed
temperature of heat generated by the fuel-fired burner 20, 22 is
within the predetermined temperature control range (i.e., less than
the upper limit and greater than the lower limit). If the
temperature of the heat generated by the fuel-fired burner 20, 22
is within the predetermined temperature control range, the control
routine 200 loops back to step 202 to continue monitoring the
output from the control temperature sensor 184. However, if the
temperature of the heat generated by the fuel-fired burner 20, 22
is not within the predetermined temperature control range, a
control signal is generated and the control routine 200 advances to
step 206 if the temperature of the heat generated by the fuel-fired
burner 20, 22 is above the upper control limit or step 208 if the
temperature of the heat generated by the fuel-fired burner 20, 22
is below the lower control limit.
[0097] In step 206, the electronic controller 76 decreases the fuel
being supplied to the fuel-fired burner 20, 22. To do so, the
electronic controller 76 increases the air-to-fuel ratio of the
air/fuel mixture being supplied to the burner 20, 22 by reducing
the amount of fuel being injected into the mixing chamber 146 by
the fuel injectors 132, 134. For example, to decrease the fuel
being supplied to the fuel-fired burner 20, the electronic
controller 76 generates a control signal on the signal line 136
that reduces the amount of fuel being injected by the fuel injector
132 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 20 via the fuel line 148. Similarly, to decrease the fuel
being supplied to the fuel-fired burner 22, the electronic
controller 76 generates a control signal on the signal line 138
that reduces the amount of fuel being injected by the fuel injector
134 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 22 via the fuel line 150. Once the fuel being supplied to
the fuel-fired burner 20, 22 has been decreased, the control
routine advances to step 210.
[0098] In step 210, the electronic controller 76 determines if the
out-of-range condition in step 206 is a repeat occurrence. More
specifically, the controller 76 determines if a predetermined
number of temperature readings have been outside of the temperature
control range. In particular, the electronic controller 76 monitors
the results of previous fuel adjustments to determine if the
fuel-fired burner 20, 22 has returned to operation within the
predetermined temperature control range. If the controller 76
determines that a predetermined number of temperature readings have
been outside of the temperature control range, the electronic
controller 76 concludes that the fuel-fired burner 20, 22 cannot be
brought back into control, an error signal is generated, and the
control routine 200 advances to step 212. Otherwise, the control
routine 200 loops back to step 202 to continue monitoring operation
of the fuel-fired burner 20, 22 during filter regeneration.
[0099] In step 212, the electronic controller 76 shuts down the
fuel-fired burner 20, 22. In particular, since the electronic
controller 76 concluded in step 210 that the fuel-fired burner 20,
22 cannot be brought back into control, the controller 76 ceases to
supply fuel to the affected burner 20, 22, ceases to generate a
spark between the electrodes 48, 50, or otherwise ceases operation
of the affected burner 20, 22.
[0100] Referring back to step 204, if the temperature of the heat
generated by the fuel-fired burner 20, 22 is below the lower
control limit, the control routine advances to step 208. In step
208, the electronic controller 76 increases the fuel being supplied
to the fuel-fired burner 20, 22. To do so, the electronic
controller 76 decreases the air-to-fuel ratio of the air/fuel
mixture being supplied to the burner 20, 22 by increasing the
amount of fuel being injected into the mixing chamber 146 by the
fuel injectors 132, 134. For example, to increase the fuel being
supplied to the fuel-fired burner 20, the electronic controller 76
generates a control signal on the signal line 136 that increases
the amount of fuel being injected by the fuel injector 132 into the
mixing chamber 146 thereby decreasing the air-to-fuel ratio of the
air/fuel mixture being supplied to the fuel-fired burner 20 via the
fuel line 148. Similarly, to increase the fuel being supplied to
the fuel-fired burner 22, the electronic controller 76 generates a
control signal on the signal line 138 that increases the amount of
fuel being injected by the fuel injector 134 into the mixing
chamber 146 thereby decreasing the air-to-fuel ratio of the
air/fuel mixture being supplied to the fuel-fired burner 22 via the
fuel line 150. Once the fuel being supplied to the fuel-fired
burner 20, 22 has been increased, the control routine advances to
step 210 to determine if control of the fuel-fired burner has been
regained in the manner previously discussed.
[0101] Output from the outlet temperature sensor 186 may also be
utilized by the electronic controller 76 to control operation of
the fuel-fired burner 20, 22 during regeneration of the particulate
filter 24, 26. In particular, as shown in FIG. 11, a control
routine 250 may be executed by the electronic controller 76 during
filter regeneration. The control routine 250 begins with step 252
in which the electronic controller 76 determines the temperature at
the outlet of the particulate filter 24, 26. In particular, the
electronic controller 76 scans or otherwise reads the signal line
192 to monitor output from the outlet temperature sensor 186. Once
the electronic controller 76 has determined the temperature at the
outlet of the particulate filter 24, 26, the routine 250 advances
to step 254.
[0102] In step 254, the electronic controller 76 determines if the
sensed filter outlet temperature is above a predetermined upper
temperature limit. If the filter outlet temperature is below the
upper temperature limit, the control routine 250 loops back to step
252 to continue monitoring output from the outlet temperature
sensor 186. However, if the filter outlet temperature is above the
upper control limit, the control routine 250 advances to step
256.
[0103] In step 256, the electronic controller 76 shuts down the
fuel-fired burner 20, 22. In particular, since the electronic
controller 76 concluded in step 254 that the filter outlet
temperature was above the upper control limit, the controller 76
ceases to supply fuel to the affected burner 20, 22, ceases to
generate a spark between the electrodes 48, 50, or otherwise ceases
operation of the affected burner 20, 22. The control routine 250
then advances to step 258.
[0104] In steps 258 and 260, the electronic controller 76
determines if the filter outlet temperature has cooled to a
temperature below the upper control limit. In particular, in step
258 the electronic controller 76 scans or otherwise reads the
signal line 192 to monitor output from the outlet temperature
sensor 186 to determine the temperature at the outlet of the
particulate filter 24, 26. Once the electronic controller 76 has
determined the temperature at the outlet of the particulate filter
24, 26, the routine 250 advances to step 260.
[0105] In step 260, the electronic controller 76 determines if the
sensed filter outlet temperature is still above the predetermined
upper temperature limit. If the filter outlet temperature is still
above the upper control limit, the control routine 250 loops back
to step 258 to continue monitoring output from the outlet
temperature sensor 186. However, if the filter outlet temperature
is now below the upper temperature limit, the control routine 250
advances to step 262.
[0106] In step 262, the electronic controller 76 restarts the
fuel-fired burner 20, 22. In particular, since the electronic
controller 76 concluded in step 260 that the filter outlet
temperature is now below the upper control limit, the controller 76
commences to supply fuel to the affected burner 20, 22, generates
the spark between the electrodes 48, 50, and otherwise re-commences
operation of the affected burner 20, 22. The control routine 250
then loops back to step 252 to monitor operation of the burner 20,
22.
[0107] The electronic controller 76 also monitors the output of a
number of pressure sensors associated with the soot abatement
assemblies 14, 16. For example, each of the soot abatement
assemblies 14, 16 includes a filter inlet pressure sensor 264 and a
filter outlet pressure sensor 266 (see FIG. 8). The pressure
sensors 264 and 266 are electrically coupled to the electronic
controller 76 via signal lines 268 and 270, respectively. The
pressure sensors 264, 266 may be embodied as any type of pressure
sensing device such as, for example, commercially available
pressure transducers.
[0108] Regeneration of the particulate filters 24, 26 may be
commenced as a function of output from the pressure sensors 264,
266. For example, the pressure sensors 264, 266 may be utilized to
sense the pressure difference across the particulate filter 24, 26
(i.e., the "pressure drop" across the filter) to determine when the
filter 24, 26 requires regeneration. Specifically, when the
pressure drop across one of the particulate filters 24, 26
increases to a predetermined value, the filter regeneration process
may be commenced for that particular filter 24, 26. It should be
appreciated that the pressure sensors 264, 266 may be embodied as a
single sensor. In particular, a single sensor which measures a
differential pressure may be used. Such sensors have two input
ports, one of which measures pressure upstream of the filter, the
other of which measures pressure downstream of the filter. In
operation, such a sensor measures the pressure difference between
its ports and generates an output relating to the same. Moreover,
it should also be appreciated that in certain embodiments, a single
pressure sensor on either side of particulate filter 24, 26 may be
utilized. In such a configuration, output from the single pressure
sensor is monitored to determine when pressure exceeds a
predetermined upper threshold or is below a predetermined lower
threshold (as opposed to monitoring the pressure drop across the
filter).
[0109] It should be appreciated that the control scheme utilized to
initiate filter regeneration may be designed in a number of
different manners. For example, a timing-based control scheme may
be utilized in which the regeneration of the particulate filters
24, 26 is commenced as a function of time. For instance,
regeneration of particulate filters 24, 26 may be performed at
predetermined timed intervals.
[0110] The output from the pressure sensors 264, 266 may also be
used in conjunction with other information to trigger regeneration
of the particulate filters 24, 26. For example, the pressure drop
across the filter 24, 26, as a function of the exhaust mass flow
from the engine 80, may be used to trigger filter regeneration. To
do so, a data table (e.g., a map) of the particulate filter 24, 26
is first experimentally generated. To generate such a map, the
pressure drop across the filter 24, 26 as a function of exhaust
mass flow at various particulate (soot) loadings is mapped.
Specifically, the filter 24, 26 is first impregnated with a given
amount of soot. Such an amount of soot may be indicative of a
desired loading that would necessitate regeneration. For instance,
if it is desirable to regenerate a particular type of particulate
filter 24, 26 when it is loaded with, for example, 5.0 grams/liter,
the filter being utilized to experimentally generate the map is
first pre-loaded with such an amount of soot (i.e., 5.0
grams/liter). Once pre-loaded, the pressure drop across the filter
is experimentally measured at a plurality different exhaust mass
flows. A lookup table (e.g., a map) can then be generated which
includes a plurality of the experimentally derived pressure drop
values each of which corresponds to one of the plurality of
different exhaust mass flow values. Such a map may be programmed
into the controller 76.
[0111] The map of such experimentally derived pressure drop values
may then be used to determine when to trigger regeneration. In
particular, during operation of the engine 80, the controller 76
may determine the current pressure drop across the filter 24, 26
and exhaust mass flow from the engine 80. As described herein, the
pressure drop may be determined by monitoring output from the
pressure sensors 264, 266. As described in greater detail below,
the controller 76 may determine exhaust mass flow by monitoring the
output from a mass flow sensor 892 (see FIG. 8), such as a hot wire
mass flow sensor. It should be appreciated that the controller 76
may communicate with the mass flow sensor 892 directly, or may
obtain the output from the sensor 892 from the engine control unit
78 via a CAN interface 314 (the CAN interface 314 is described in
greater detail below). Alternatively, exhaust mass flow may be
calculated by the controller 76 in a conventional manner by use of
engine operation parameters such as engine RPM, turbo boost
pressure, and intake manifold temperature (along with other known
parameters such as engine displacement). It should be appreciated
that the controller 76 may itself calculate the mass flow, or may
obtain the calculated mass flow from the engine control unit 78 via
the CAN interface 314.
[0112] Once the controller 76 has determined both the pressure drop
across the particulate filter 24, 26 and the exhaust mass flow from
the engine 80, the controller 76 queries the lookup table (i.e.,
the map) to retrieve the experimentally created limit value which
corresponds to the sensed (or calculated) exhaust mass flow of the
engine 80. The controller 76 then compares the sensed pressure drop
across the particulate filter 24, 26 to the retrieved limit value.
If the sensed pressure drop across the filter 24, 26 exceeds the
retrieved limit value, the controller 76 determines that the filter
24, 26 is in need of regeneration and commences a regeneration
cycle.
[0113] An exemplary control routine 860 for triggering filter
regeneration based on the pressure drop across the filter as a
function of exhaust mass flow is shown in FIG. 34. The routine 860
commences with step 862 in which the electronic controller 76
determines the pressure drop (.DELTA.P) across the particulate
filter 24, 26. Specifically, the controller 76 monitors the output
from the pressure sensors 264, 266 and thereafter calculates the
pressure drop (.DELTA.P) across the filter. The control routine 860
then advances to step 864.
[0114] In step 864, the controller 76 determines the exhaust mass
flow from the engine 80. As described above, the controller 76 may
determine the exhaust mass flow by monitoring the output from the
mass flow sensor 892, or by calculating it with the use of engine
operation parameters such as engine RPM, turbo boost pressure, and
intake manifold temperature (along with other known parameters such
as engine displacement). In either case, once the controller
determines the exhaust mass flow, the control routine advances to
step 866.
[0115] In step 866, the controller 76 queries the lookup table
(i.e., the filter map) to retrieve the experimentally created limit
value which corresponds to the sensed (or calculated) exhaust mass
flow (as determined in step 864). Once the controller 76 has
retrieved the limit value from the lookup table, the control
routine 860 advances to step 868.
[0116] In step 868, the controller 76 compares the sensed pressure
drop across the particulate filter 24, 26 (as determined in step
862) to the retrieved limit value. If the sensed pressure drop
across the filter 24, 26 exceeds the retrieved limit value, the
controller 76 concludes that the filter 24, 26 is in need of
regeneration, and the control routine 860 advances to step 870. If
the sensed pressure drop across the filter 24, 26 does not exceed
the retrieved limit value, the control routine 860 loops back to
step 860 to continue monitoring accumulation in the filter 24,
26.
[0117] In step 870, the controller 76 commences filter
regeneration. Specifically, the electronic controller 76 operates
the fuel-fired burner 20, 22 to regenerate the particulate filter
24, 26 in any of the numerous manners described herein. Once filter
regeneration is complete, the control routine 870 ends.
[0118] The output from the pressure sensors 264, 266 may also be
utilized to monitor performance of the engine 80. In particular,
characteristics of soot accumulation within the particulate filters
24, 26 may be indicative of certain engine performance
characteristics. For example, excessive or otherwise irregular soot
accumulation in the particulate filters 24, 26 may be indicative of
excessive oil usage by the engine 80. Excessive or otherwise
irregular soot accumulation in the particulate filters 24, 26 may
also be indicative of a stuck or leaky engine fuel injector. The
electronic controller 76 may be configured to monitor and analyze
the output from the pressure sensors 264, 266 to determine if any
such engine conditions exist.
[0119] It should be appreciated that if a given design utilizes
methods or devices other than pressure sensors to determine soot
accumulation within the particulate filters 24, 26, the output from
such methods or devices may be monitored and analyzed to determine
if any such engine conditions exist. As such, although an exemplary
embodiment of a control scheme for monitoring engine performance as
a function of soot accumulation in the filters 24, 26 based on
output from the pressure sensors 264, 266 will now be described in
greater detail, it should be appreciated that such a description is
not intended to be limited to only pressure sensor-based
systems.
[0120] Referring now to FIG. 12, there is shown an exemplary
embodiment of a control routine 300 for monitoring engine
performance as a function of soot accumulation within the
particulate filters 24, 26. The routine commences with step 302 in
which the electronic controller 76 determines the rate of soot
accumulation within the particulate filters 24, 26. In particular,
during operation of the engine 80, the pressure drop across the
particulate filters 24, 26 (.DELTA.P) is continuously monitored by
the controller 76. Specifically, at a predetermined frequency, the
output from pressure sensors 264, 266 is read so that the pressure
drop (.DELTA.P) may be calculated and thereafter stored in a table
in a memory device (e.g., RAM or other memory device associated
with the electronic controller 82). Over time, the pressure drop
(.DELTA.P) may be tracked. For example, a graphical representation
which tracks the pressure drop (.DELTA.P) across one of the filters
24, 26 as a function of time is shown in FIG. 13. In the exemplary
embodiment described herein, the rate of soot accumulation may be
determined by tracking the pressure drop (.DELTA.P) over time as
indicated with the line 312 in the graphical representation of FIG.
13. Once the electronic controller 76 has determined the rate of
soot accumulation within the soot particulate filter 24, 26, the
routine 300 advances to step 304.
[0121] In step 304, the electronic controller 76 analyzes the rate
of soot accumulation within the particulate filter 24, 26. In the
exemplary embodiment described herein, the controller 76 analyzes
the rate of soot accumulation within the particulate filter 24, 26
by analyzing the slope of the line 312 generated by tracking the
pressure drop (.DELTA.P) over time. For example, if the slope of
the line 312 remains relatively constant (i.e., within
predetermined limits deemed to be indicative of a constant slope),
such as indicated with a dashed line in FIG. 13, the electronic
controller 76 concludes that there is no change in the rate in
which soot is accumulating within particulate filter 24, 26.
However, if the slope of the line 312 increases beyond
predetermined limits (as shown in the solid line in FIG. 13), the
electronic controller 76 concludes that there is a change in the
rate in which soot is accumulating within the particulate filter
24, 26. It should be appreciated that other methods may be utilized
to analyze the rate of soot accumulation within the filter 24, 26
with the method described herein being merely exemplary in nature.
Once the electronic controller 76 has analyzed the soot
accumulation within the particulate filter 24, 26, the control
routine 300 advances to step 306.
[0122] In step 306, the electronic controller 76 determines if the
rate of soot accumulation within particulate filter 24, 26 is
indicative of a predetermined engine condition. Specifically, a
lookup table stored in the in the memory device 84 (or other memory
device associated with the electronic controller 82) may be queried
to determine if the rate of soot accumulation, as analyzed in step
304, matches predetermined criteria. For example, the contents of
the lookup table are used to determine if the analysis of step 304
is indicative of no change in the rate of soot accumulation or
change that is within predetermined acceptable limits. If so, the
controller 76 concludes that the rate of soot accumulation is not
indicative of an engine condition, and the control routine loops
back to step 302 to continue monitoring soot accumulation within
the filters 24, 26. The contents of the lookup table may also be
used to determine if the analysis performed in step 304 is
indicative of change in the rate of soot accumulation that is
outside of predetermined limits. If so, the controller 76 concludes
that the rate of soot accumulation may be indicative of an engine
condition, and the control routine 300 advances to step 308.
[0123] In step 308, the electronic controller 76 generates an error
signal. For example, the electronic controller 76 may generate an
output signal which causes a visual, audible, or other type of
alarm to be generated for presentation to the operator (e.g., the
driver of the truck 12). The error signal may simply cause an
electronic log or the like to be updated with information
associated with the filter analysis of steps 302-306.
[0124] As indicated in step 310, the error signal may be
communicated to the engine control unit (ECU) 78 associated with
the engine 80. The details of doing so will now be described in
greater detail. However, it should be appreciated that such a
description is not limited to communication of the error signal
generated in step 308 of the control routine 300, but rather any
error signal herein described (along with any other error signal
generated by the controller 76) may be communicated to the engine
control unit 78. Moreover, as will be discussed herein in greater
detail, the engine control unit 78 may communicate information,
such as engine operation information, to the controller 76.
[0125] In a conventional manner, engine systems, such as the engine
80 of the truck 12, include an engine control unit which is, in
essence, the master computer responsible for interpreting
electrical signals sent by engine sensors and for activating
electronically-controlled engine components to control the engine.
For example, an engine control unit is operable to, amongst many
other things, determine the beginning and end of each injection
cycle of each engine cylinder, or determine both fuel metering and
injection timing in response to sensed parameters such as engine
crankshaft position and RPM, engine coolant and intake air
temperature, and absolute intake air boost pressure.
[0126] Error signals generated by the controller 76 (or subsequent
signals generated in response the error signal) may be communicated
to the engine control unit 78. Specifically, the electronic
controller 76 of the emission abatement assembly 10 may be
configured to communicate with the engine control unit 78 via an
interface 314. The interface 314 may be any type of communication
interface which enables electronic communication between the
electronic controller 76 and the engine control unit 78. One type
of interface which is suitable for use as the interface 314 is a
Controller Area Network or "CAN" interface. A CAN interface is a
serial bus network of microcontrollers that connects devices,
sensors and actuators in a system or sub-system for real-time
control applications. Details of a CAN interface, which was first
developed by Robert Bosch GmbH in 1986, are documented in ISO 11898
(for applications up to 1 Mbps) and ISO 11519 (for applications up
to 125 Kbps), both of which are hereby incorporated by
reference.
[0127] By use of the CAN interface 314, information such as engine
RPM and turbo boost pressure may be obtained from the engine
control unit 78 for use by the electronic controller 76. Such
information may be used by the controller 76 in the execution of
certain control routines. By using information from the engine
control unit 78, a redundant sensor array to determine such
information solely for use by the electronic controller is
eliminated.
[0128] Moreover, the CAN interface 314 allows for the transfer of
error signals (e.g., error flags) or the like to the engine control
unit 78 for use by the engine control unit 78 during its operation.
For example, an error signal indicative of an engine problem (as
described in regard to the control routine 300) may be communicated
to the engine control unit 78. Armed with this information, the
engine control unit 78 may be programmed to perform additional
engine analysis, generate an error signal to the truck operator
(e.g., an indicator light on the truck's instrument cluster), or
store the error message in an error log which can be accessed by a
service technician. The CAN interface 314 also allows an engine
manufacturer to assume some degree of control over the operation of
the emission abatement assembly 10, if desired.
[0129] As such, it should be appreciated that the controller 76 of
the control unit 18 monitors operation of the fuel-fired burners
20, 22 (and other components of the emission abatement assembly 10)
to determine if any of the predetermined conditions described
herein (or other conditions) are met. The controller 76 may then
generate a signal, such as an error signal, indicative of such
conditions and communicate such a signal to the engine control unit
78 via the CAN interface 314. Moreover, the CAN interface 314 may
be used by the engine control unit 78 to communicate information,
such as information relating to engine operation, to the controller
76. For example, information relating to engine RPM or turbo boost
pressure may be communicated to the controller 76 via the CAN
interface 314. In addition to engine operation information, if so
configured, the engine control unit 78 may also generate and
communicate control signals for controlling operation of the
fuel-fired burners 20, 22 to the controller 76. For example, the
engine control unit 78 may be programmed to initiate regeneration
cycles of the particulate filters 24, 26. In such a case, the
engine control unit 78 may generate and communicate a control
signal to the controller 76 which causes the controller 76 to
commence regeneration of one of the particulate filters 24, 26.
[0130] As shown in FIG. 29, the electronic controller 76 of the
control unit 18 may be integrated with the engine control unit 78.
As such, in addition to controlling operation of the engine 80, the
engine control unit 78 also controls operation of the emission
abatement assembly 10. In such a way, the engine control unit 78 is
also, in essence, the master computer responsible for interpreting
electrical signals sent by sensors associated with the emission
abatement assembly 10 and for activating electronically-controlled
components associated with the emission abatement assembly 10. For
example, the engine control unit 78 is operable to, amongst many
other things, determine the beginning and end of each filter
regeneration cycle, determine the amount and ratio of fuel and air
to be introduced into the fuel-fired burners 20, 22, along with the
other functions herein described as being performed by the
controller 76 of the emission abatement assembly 10.
[0131] To do so, the engine control unit 78 includes a number of
electronic components commonly associated with electronic units
which are utilized in the control of engine systems. For example,
the engine control unit 78 may include, amongst other components
customarily included in such devices, a processor such as a
microprocessor 728 and a memory device 730 such as a programmable
read-only memory device ("PROM") including erasable PROM's (EPROM's
or EEPROM's).
[0132] The memory device 730 is provided to store, amongst other
things, instructions in the form of, for example, a software
routine (or routines) which, when executed by the processing unit,
allows the engine control unit 78 to control operation of both the
engine 80 and the emission abatement assembly 10. To do so, as
shown in FIG. 29, the engine control unit 78 is electrically
coupled to both the engine 80 and the emission abatement assembly
10. In particular, the engine control unit 78 is electrically
coupled to the engine 80 via the signal line 718, whereas the
engine control unit 78 is electrically coupled to the emission
abatement assembly 10 via the signal line 720. Although each is
shown schematically as a single line, it should be appreciated that
the signal lines 718, 720 may be configured as any type of signal
carrying assembly which allows for the transmission of electrical
signals in either one or both directions between the engine control
unit 78 and the engine 80 or the emission abatement assembly 10,
respectively. For example, either one or both of the signal lines
718, 720 may be embodied as a wiring harness having a number of
signal lines which transmit electrical signals between the engine
control unit 78 and the engine 80 or the emission abatement
assembly 10, respectively. In such an arrangement, signals
generated by operation of a number of engine sensors 734 or the
sensors 736 associated with the emission abatement assembly 10 are
transmitted to the engine control unit 78 via the corresponding
wiring harness, and signals generated by the engine control unit 78
are transmitted to the engine 80 or the emission abatement assembly
10 by the corresponding wiring harness. It should be appreciated
that any number of other wiring configurations may be used. For
example, individual signal wires may be used, or a system utilizing
a signal multiplexer may be used for the design of either one or
both of the signal lines 718, 720. Moreover, the signal lines 718,
720 may be integrated such that a single harness or system is
utilized to electrically couple both the engine 80 and the emission
abatement assembly 10 to the engine control unit 78.
[0133] The engine control unit 78 also includes an analog interface
circuit 732. The analog interface circuit 732 converts the output
signals from the various analog engine sensors 734 and the emission
abatement sensors 736 into a signal which is suitable for
presentation to an input of the microprocessor 728. In particular,
the analog interface circuit 732, by use of an analog-to-digital
(A/D) converter (not shown) or the like, converts the analog
signals generated by the sensors 734, 736 into a digital signal for
use by the microprocessor 728. It should be appreciated that the
A/D converter may be embodied as a discrete device or number of
devices, or may be integrated into the microprocessor 728. It
should also be appreciated that if any one or more of the sensors
734, 736 generate a digital output signal, the analog interface
circuit 732 may be bypassed.
[0134] It should be appreciated that the emission abatement sensors
736 communicating with the engine control unit 78 may be any of the
sensors herein described in relation to the emission abatement
assembly 10. For example, the pressure sensors 264, 266 and the
temperature sensors 182, 184, 186 associated with the soot
abatement assemblies 14, 16 may be coupled to the engine control
unit 78. Moreover, the sensors and detectors 164, 426, 460, 510 of
the control unit 18 may be coupled to the engine control unit
78.
[0135] The analog interface circuit 732 also converts signals from
the microprocessor 728 into an output signal which is suitable for
presentation to the electrically-controlled components 744
associated with the engine 80 and the electronically-controlled
components 746 associated with the emission abatement assembly 10.
In particular, the analog interface circuit 732, by use of a
digital-to-analog (D/A) converter (not shown) or the like, converts
the digital signals generated by the microprocessor 728 into analog
signals for use by the electronically-controlled components 744
associated with the engine such as the fuel injector assembly,
ignition assembly, fan assembly, etcetera, along with analog
signals for use by electronically-controlled components 746
associated with the emission abatement assembly 10 such as the pump
motor 92, the air valve 102, the fuel injectors 132, 134, the
valves 140, 154, 156, the igniters 170, 172, etcetera. It should be
appreciated that, similar to the A/D converter described above, the
D/A converter may be embodied as a discrete device or number of
devices, or may be integrated into the microprocessor 728. It
should also be appreciated that if any one or more of the
electronically-controlled components 744 associated with the engine
80 or electronically-controlled components 746 associated with the
emission abatement assembly 10 operate on a digital input signal,
the analog interface circuit 732 may be bypassed.
[0136] Hence, the engine control unit 78 may be operated to control
operation of both the engine 80 and the emission abatement assembly
10. In particular, the engine control unit 78 operates in a
closed-loop control scheme in which the engine control unit 78
monitors outputs of the sensors 734, 736 in order to control the
inputs to the controlled components 744, 746 thereby managing the
operation of both the engine 80 and the emission abatement assembly
10. In particular, the engine control unit 78 communicates with the
sensors 734 in order to determine, amongst numerous other things,
the engine coolant temperature, manifold air pressure,
crankshaft/flywheel position and speed, and the amount of oxygen in
the exhaust gas. Armed with this data, the engine control unit 78
performs numerous calculations each second, including looking up
values in preprogrammed tables, in order to execute routines to
perform such functions as varying spark timing or determining how
long the fuel injector is to be left open in a particular
cylinder.
[0137] Contemporaneous with such control of the engine 80, the
engine control unit 78 also executes a routine for controlling
operation of the emission abatement assembly 10. In particular, the
engine control unit 78 communicates with the sensors 736 in order
to determine, amongst numerous other things, the soot accumulation
level in the particulate filters, various temperature and pressure
readings, etcetera. Armed with this data, the engine control unit
78 performs numerous calculations each second, including looking up
values in preprogrammed tables, in order to execute algorithms to
perform such functions as supplying fuel and air to the fuel-fired
burners 20, 22, energizing the electrodes 48, 50, etcetera.
[0138] As such, the engine control unit 78 controls operation of
both the engine 80 and the emission abatement assembly 10. In
particular, during operation of the engine 80, the engine control
unit 78 executes a fuel injector control routine which, amongst
other things, generates a number of injection signals in the form
of injection pulses which are communicated to the individual
injectors of the engine's fuel injector assembly. In response to
receipt of the injection pulse, a fuel injector is opened for a
predetermined period of time, thereby injecting fuel into the
corresponding cylinder of the engine 80. Contemporaneous with
execution of the fuel injection routine, the engine control unit 78
executes a burner control routine which, amongst other things,
generates a number of control signals which are communicated to the
various electronically-controlled components 746 associated with
the emission abatement assembly 10, thereby controlling operation
of the fuel-fired burners 20, 22. For example, signals are
generated and communicated for, amongst other things, varying the
amount of fuel being supplied to the fuel-fired burner 20, 22,
energizing the electrodes 48, 50, etcetera.
[0139] Moreover, the engine control unit 78 also monitors input
from the various sensors 736 associated with the emission abatement
assembly 10 in order to utilize such input in the closed-loop
control of the assembly 10. For example, signals communicated to
the engine control unit 78 are utilized to monitor the temperature
of certain areas within the soot abatement assembly 14, 16, the
pressure drop across the particulate filter 24, 26, along with the
numerous other functions herein described.
[0140] It should be appreciated that such routines (i.e., the fuel
injector control routine and the fuel reformer control routine) may
be embodied as separate software routines, or may be combined as a
single software routine.
[0141] Referring now to FIG. 14, there is shown a control routine
350 for monitoring ash buildup in the particulate filters 24, 26.
Over time as multiple filter regenerations occur, ash may
accumulate in the particulate filters 24, 26. By monitoring (e.g.,
measuring and data logging) the pressure drop (.DELTA.P) across the
particulate filter 24, 26 subsequent to each filter regeneration
process, it can be determined when the filter requires the ash to
be cleaned. Specifically, as will herein be described in greater
detail, shortly after each filter regeneration cycle, the pressure
drop (.DELTA.P) across the particulate filter 24, 26 is obtained
and stored in memory. Once the pressure drop (.DELTA.P) across the
particulate filter 24, 26 exceeds a predetermined upper limit, an
error signal indicative of the need to service the filter by
removing the ash from the filter is generated.
[0142] The control routine 350 commences with step 352 in which the
electronic controller 76 regenerates one of the particulate filters
24, 26. Specifically, as described in greater detail herein, the
electronic controller 76 operates the fuel-fired burner 20, 22 to
generate heat to regenerate the particulate filter 24, 26. Once the
regeneration cycle is complete, the control routine 350 advances to
step 354.
[0143] In step 354, the electronic controller 76 measures the
pressure drop (.DELTA.P) across the recently regenerated
particulate filter 24, 26. Specifically, the output from pressure
sensors 264, 266 of the recently regenerated filter is read so that
the pressure drop (.DELTA.P) may be calculated.
[0144] Thereafter, the control routine advances to step 356 where
the value of the pressure drop (.DELTA.P) across the recently
regenerated particulate filter 24, 26 is stored in a table in a
memory device (e.g., RAM or other memory device associated with the
electronic controller 82). The control routine 350 then advances to
step 358.
[0145] In step 358, the electronic controller 76 determines if the
pressure drop (.DELTA.P) across the recently regenerated
particulate filter 24, 26 is above a predetermined upper limit. If
the pressure drop (.DELTA.P) across the recently regenerated
particulate filter 24, 26 is below the upper limit, the control
routine 350 ends until reinitiated subsequent to completion of the
next filter regeneration cycle. However, if the pressure drop
(.DELTA.P) across the recently regenerated particulate filter 24,
26 is above the upper control limit, the control routine 350
advances to step 360.
[0146] In step 360, the electronic controller 76 generates an error
signal. For example, the electronic controller 76 may generate an
output signal which causes a visual, audible, or other type of
alarm to be generated for presentation to the operator (e.g., the
driver of the truck 12). Alternatively, the error signal may simply
cause an electronic log or the like to be updated with information
associated with the filter analysis of steps 352-358. It should be
appreciated that the error signal generated in step 360 may be
configured for use with any type of alarming or error tracking
arrangement to fit the needs of a given system design.
[0147] As indicated in step 362, if the electronic controller 76 is
so equipped, the error signal (or a subsequent signal generated in
response the error signal) may be communicated to the engine
control unit 78 via the CAN interface 314. Armed with this
information, the engine control unit 78 may be programmed to
perform additional filter analysis, generate an error signal to the
truck operator (e.g., an indicator light on the truck's instrument
cluster) indicating that the affected filter(s) 24, 26 requires
servicing (i.e., ash removal), or store the error message in an
error log which can be accessed by a service technician. The
control routine 350 then ends.
[0148] As described above, the electronic controller 76 may use a
number of different control schemes to determine when one of the
particulate filters 24, 26 is in need of regeneration. For example,
a sensor-based scheme or a timing-based scheme may be utilized. In
either case, when the controller 76 determines that one of the
filters 24, 26 is in need of regeneration, a regeneration cycle is
commenced in which the electronic controller 76 operates the
fuel-fired burners 14, 16 to regenerate the filters 24, 26,
respectively. To do so, the air pump 90 and the air valve 102 are
operated to supply combustion air to the appropriate burner 20, 22.
Contemporaneously, fuel is supplied to the appropriate burner 20,
22 via the fuel delivery assembly 120. In particular, to supply
fuel to the fuel-fired burner 20, the fuel injector 132 is operated
to inject fuel into the mixing chamber 146 where it is atomized in
a flow of atomization air being supplied to the mixing chamber 146
by the air valves 154, 156. The resultant air/fuel mixture is
conducted to the fuel inlet nozzle 54 of the fuel-fired burner 20
via the fuel line 148. On the other hand, to supply fuel to the
fuel-fired burner 22, the fuel injector 134 is operated to inject
fuel into the mixing chamber 146 where it is atomized in the flow
of atomization air being supplied to the mixing chamber 146 by the
air valves 154, 156. The resultant air/fuel mixture is conducted to
the fuel inlet nozzle 54 of the fuel-fired burner 22 via the fuel
line 150.
[0149] The air/fuel mixture entering the burner 20, 22 via the fuel
inlet nozzle 54 is ignited by the electrodes 48, 50. In the case of
operation of the fuel-fired burner 20, the igniter 170 is actuated
to generate a spark across the electrode gap 52 between the
electrodes 48, 50 of the burner 20 thereby igniting the air/fuel
mixture exiting the fuel inlet 54. In the case of operation of the
fuel-fired burner 22, the igniter 172 is actuated to generate a
spark across the electrode gap 52 between the electrodes 48, 50 of
the burner 22 thereby igniting the air/fuel mixture exiting the
fuel inlet 54.
[0150] As described above, the electronic controller 76 monitors
output from the flame temperature sensor 182 to detect or otherwise
determine presence of an ignition flame in the combustion chamber
34 of the fuel-fired burner 20, 22 being activated. Specifically,
when the electronic controller 76 initiates ignition of the
fuel-fired burner 20, 22, the controller 76 monitors output from
the flame temperature sensor 182 to ensure that the air/fuel
mixture entering the burner 20, 22 is being ignited by the spark
from the electrodes 48, 50. An error signal is generated if the
output of the flame temperature sensor does not meet a
predetermined criteria.
[0151] Once the fuel-fired burner 20, 22 is activated, it begins to
produce heat. Such heat is directed downstream (relative to exhaust
gas flow) and into contact with the upstream face of the
particulate filter 24, 26. The heat ignites and burns soot
particles trapped in the filter substrate 60 thereby regenerating
the particulate filter 24, 26. Illustratively, heat in the range of
600-650 degrees Celsius may be sufficient to regenerate a
non-catalyzed filter, whereas heat in the range of 300-350 degrees
Celsius may be sufficient to regenerate a catalyzed filter.
[0152] In an illustrative embodiment, regeneration of the
particulate filter 24, 26 may take only a few minutes. Moreover, it
should be appreciated that regeneration of the particulate filter
24, 26 may be self-sustaining once initiated by heat from the
fuel-fired burner 20, 22, respectively. Specifically, once the
filter 24, 26 is heated to a temperature at which the soot
particles trapped therein begin to ignite, the ignition of an
initial portion of soot particles trapped therein can cause the
ignition of the remaining soot particles much in the same way a
cigar slowly burns from one end to the other. In essence, as the
soot particles "burn," an amount of heat is released in the "burn
zone." Locally, the soot layer (in the burn zone) is now much
hotter than the immediate surroundings. As such, heat is
transferred to the as yet un-ignited soot layer downstream of the
burn zone. The energy transferred may be sufficient to initiate
oxidation reactions that raise the un-ignited soot to a temperature
above its ignition temperature. As a result of this, heat from the
fuel-fired burners 20, 22 may only be required to commence the
regeneration process of the filter 24 (i.e., begin the ignition
process of the soot particles trapped therein).
[0153] During the regeneration cycle, the fuel-fired burners 20, 22
may be controlled in the manner described herein in regard to FIGS.
9-11. Specifically, the control routines 200 and 250 may be
utilized to monitor temperatures within soot abatement assemblies
14, 16 in the manner described herein.
[0154] Referring now to FIGS. 30 and 31, there is shown a control
routine 750 for starting up the fuel-fired burners 20, 22 during
commencement of a regeneration cycle. The routine begins with step
752 in which the routine determines if a request to startup the
fuel-fired burner 20, 22 (i.e., a burner startup request) has been
executed. It should be appreciated that a burner startup request
may take many different forms including, for example, a startup
request generated by a software control routine in response to
sensed, timed, or otherwise determined indication that one of the
particulate filters 24, 26 is in need of regeneration. For example,
a sensor-based scheme, map-based scheme, or a timing-based scheme
may be utilized to generate a startup request. As such, in step
752, if the control routine 750 detects a burner startup request, a
control signal is generated and the routine 750 advances to step
754. If the control routine 750 does not detect a burner startup
request, the routine 750 loops back to step 752 to continue
monitoring for such a request.
[0155] In step 754, the electronic controller 76 supplies a
relatively high amount of fuel to the fuel-fired burner 20, 22 to
facilitate ignition of a flame in the combustion chamber 34.
Specifically, an air/fuel mixture is supplied to the burner 20, 22
where it is to be ignited by the spark between the electrodes 48,
50 in the presence of combustion air supplied by the control unit
18. The supply of this initial fuel level is shown graphically with
the arrow 764 of FIG. 31. The control routine 750 then advances to
step 756.
[0156] In step 756, the controller 76 determines if ignition has
occurred. The controller 76 may do so in any number of different
manners. For example, the electronic controller 76 may monitor
output from the flame temperature sensor 182 to detect or otherwise
determine presence of an ignition flame in the combustion chamber
34 of the fuel-fired burner 20, 22. Specifically, when the
electronic controller 76 initiates ignition of the fuel-fired
burner 20, 22, the controller 76 may monitor output from the flame
temperature sensor 182 to ensure that the air/fuel mixture entering
the burner 20, 22 is being ignited by the spark from the electrodes
48, 50. Once ignition has been detected, the control routine 750
advances to step 758. Ignition detection is shown graphically at
point 766 in FIG. 31.
[0157] In step 758, the electronic controller 76 decreases the fuel
being supplied to the fuel-fired burner 20, 22. To do so, the
electronic controller 76 increases the air-to-fuel ratio of the
air/fuel mixture being supplied to the burner 20, 22 by reducing
the amount of fuel being injected into the mixing chamber 146 by
the fuel injectors 132, 134. For example, to decrease the fuel
being supplied to the fuel-fired burner 20, the electronic
controller 76 generates a control signal on the signal line 136
that reduces the amount of fuel being injected by the fuel injector
132 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 20 via the fuel line 148. Similarly, to decrease the fuel
being supplied to the fuel-fired burner 22, the electronic
controller 76 generates a control signal on the signal line 138
that reduces the amount of fuel being injected by the fuel injector
134 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 22 via the fuel line 150.
[0158] The electronic controller 76 operates the fuel-fired burner
20, 22 at this reduced fuel level for a period of time to preheat
the components of the soot abatement assembly 14, 16. Such a
preheating period may be time-based (i.e., continue for a
predetermined period of time) or may be sensor-based (i.e.,
continue until a predetermined temperature is sensed by one or more
of the temperature sensors 182, 184, 186). The preheating period is
shown graphically with the arrow 768 of FIG. 31. Once this period
of time has elapsed (i.e., once the system has been preheated), the
control routine 750 advances to step 760.
[0159] In step 760, the electronic controller 76 ramps up or
otherwise increases the fuel being supplied to the fuel-fired
burner 20, 22. To do so, the electronic controller 76 decreases the
air-to-fuel ratio of the air/fuel mixture being supplied to the
burner 20, 22 by increasing the amount of fuel being injected into
the mixing chamber 146 by the fuel injectors 132, 134. For example,
to increase the fuel being supplied to the fuel-fired burner 20,
the electronic controller 76 generates a control signal on the
signal line 136 that increases the amount of fuel being injected by
the fuel injector 132 into the mixing chamber 146 thereby
decreasing the air-to-fuel ratio of the air/fuel mixture being
supplied to the fuel-fired burner 20 via the fuel line 148.
Similarly, to increase the fuel being supplied to the fuel-fired
burner 22, the electronic controller 76 generates a control signal
on the signal line 138 that increases the amount of fuel being
injected by the fuel injector 134 into the mixing chamber 146
thereby decreasing the air-to-fuel ratio of the air/fuel mixture
being supplied to the fuel-fired burner 22 via the fuel line
150.
[0160] In step 760, the fuel supplied to the fuel-fired burner 20,
22 may be increased at a predetermined ramp rate. For example, as
shown graphically with arrow 770 in FIG. 31, the fuel level may be
gradually increased at a predetermined ramp rate up to a specific,
predetermined fuel level, as indicated by point 772 in FIG. 31.
Such a predetermined fuel level may correspond with a desired
regeneration temperature. Once the fuel level has been ramped up,
the control routine 750 advances to step 762.
[0161] In step 762, the controller 76 adjusts the fuel level being
supplied to the fuel-fired burner 20, 22 to facilitate filter
regeneration. Specifically, as described above in regard to FIGS. 9
and 10, during a filter regeneration cycle, fueling of the burner
20, 22 is adjusted by closed-loop control. Such closed-loop control
of the fueling of the burner 20, 22 is shown generally in the area
indicated by the arrow 418 of FIG. 31. Once under closed-loop
control, the startup control routine 750 ends.
[0162] Referring now to FIG. 32, there is shown another startup
control routine 780 for starting up the fuel-fired burners 20, 22
during commencement of a regeneration cycle. The routine begins
with step 782 in which the routine 780 determines if a request to
startup the fuel-fired burner 20, 22 (i.e., a burner startup
request) has been executed. It should be appreciated that a burner
startup request may take many different forms including, for
example, a startup request generated by a software control routine
in response to sensed, timed, or otherwise determined indication
that one of the particulate filters 24, 26 is in need of
regeneration. For example, a sensor-based scheme, map-based scheme,
or a timing-based scheme may be utilized to generate a startup
request. As such, in step 782, if the control routine 780 detects a
burner startup request, a control signal is generated and the
routine 780 advances to step 784. If the control routine 780 does
not detect a burner startup request, the routine 780 loops back to
step 782 to continue monitoring for such a request.
[0163] In step 784, the controller 76 energizes the electrode
assembly of the fuel-fired burner 20, 22 that is to be regenerated
prior to any fuel being supplied to the burner. Specifically,
during startup of the fuel-fired burner 20, prior to fuel being
supplied to the burner 20, the controller 76 operates the igniter
170 to commence spark generation between the electrodes 48, 50 of
the burner 20. In the case of startup of the fuel-fired burner 22,
prior to fuel being supplied to the burner 22, the electronic
controller 76 operates the igniter 172 to commence spark generation
between the electrodes 48, 50 of the burner 22.
[0164] The controller 76 continues to energize the electrode
assembly of the fuel-fired burner 20, 22 for a predetermined period
of time prior to the introduction of fuel to the burner. The
duration of such a period of time may be configured to fit the
needs of a given system design. In particular, it has been found
that energizing the electrode assembly for such a period of time
prior to fuel introduction cleans any fouled surfaces on the
electrodes 48, 50 (i.e., removes any soot or other matter
accumulated thereon). As such, any matter accumulated on the
electrodes 48, 50 (e.g., soot, diesel fuel, water, oil, etcetera)
can be removed from the electrodes prior to the introduction of
fuel thereby enhancing operation of the fuel-fired burner 20, 22.
Once the predetermined period of time has elapsed, the control
routine 780 advances to step 786.
[0165] In step 786, the electronic controller 76 supplies fuel and
air to the fuel-fired burner 20, 22 to regenerate the particulate
filter 24, 26 in the manner described above. Specifically, an
air/fuel mixture is supplied to the burner 20, 22 where it is
ignited by the spark between the electrodes 48, 50 in the presence
of combustion air supplied by the control unit 18. Heat generated
by the combustion of the fuel regenerates the particulate filter
24, 26.
[0166] It should be appreciated that the control routines 750, 780
may be combined, if desired. For example, the electrode assembly
may be energized for a period of time (as described in step 784 of
the control routine 780) prior to the introduction of the fuel for
ignition (as described in step 754 of the control routine 750).
[0167] Referring now to FIGS. 15 and 16, there is shown a control
routine 400 for shutting down the fuel-fired burners 20, 22 during
a regeneration cycle. The control routine begins with step 402 in
which electronic controller 76 supplies fuel and air to the
fuel-fired burner 20, 22 to regenerate the particulate filter 24,
26 in the manner described above. Specifically, an air/fuel mixture
are supplied to the burner 20, 22 where it is ignited by the spark
between the electrodes 48, 50 in the presence of combustion air
supplied by the control unit 18. As described in regard to FIGS. 9
and 10, during such a filter regeneration cycle, fueling of the
burner 20, 22 is adjusted by closed-loop control. Such closed-loop
control of the fueling of the burner 20, 22 is shown generally in
the area indicated by the arrow 418 of FIG. 16.
[0168] During the filter regeneration cycle, the control routine
400, at step 404, determines if a request to shutdown the
fuel-fired burner 20, 22 (i.e., a burner shutdown request) has been
executed. It should be appreciated that a burner shutdown request
may take many different forms including, for example, a shutdown
request generated by a software control routine in response to
sensed, timed, or otherwise determined indication that the
particulate filter 20, 22 has been regenerated or that filter
regeneration is self-sustaining (as described above), an automatic
shutdown request generated by a software control routine or the
like, a timed shutdown request, or any other manual, software, or
hardware-driven shutdown request. In certain embodiments, a burner
shutdown request may be generated in response to the turning of an
ignition key associated with the engine 80 of the truck 12 from an
on position to an off position. As such, in step 404, if the
control routine 400 detects a burner shutdown request, a control
signal is generated and the routine 400 advances to step 406.
Detection of a shutdown request is shown graphically at point 420
in FIG. 16. If the control routine 400 does not detect a burner
shutdown request, the routine 400 loops back to step 402 to
continue the filter regeneration cycle.
[0169] In step 406, the electronic controller 76 decreases the fuel
being supplied to the fuel-fired burner 20, 22. To do so, the
electronic controller 76 increases the air-to-fuel ratio of the
air/fuel mixture being supplied to the burner 20, 22 by reducing
the amount of fuel being injected into the mixing chamber 146 by
the fuel injectors 132, 134. For example, to decrease the fuel
being supplied to the fuel-fired burner 20, the electronic
controller 76 generates a control signal on the signal line 136
that reduces the amount of fuel being injected by the fuel injector
132 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 20 via the fuel line 148. Similarly, to decrease the fuel
being supplied to the fuel-fired burner 22, the electronic
controller 76 generates a control signal on the signal line 138
that reduces the amount of fuel being injected by the fuel injector
134 into the mixing chamber 146 thereby increasing the air-to-fuel
ratio of the air/fuel mixture being supplied to the fuel-fired
burner 22 via the fuel line 150.
[0170] The electronic controller 76 operates the fuel-fired burner
20, 22 at this reduced fuel level for a predetermined period of
time. Such a period of time is shown graphically with the arrow 422
of FIG. 16. Once this predetermined period of time has elapsed, the
control routine advances to step 408.
[0171] In step 408, the fuel supply to the burner 20, 22 is
shutoff. Specifically, the electronic controller 76 deactuates the
fuel delivery assembly 120 thereby ceasing the supply of fuel to
the burner 20, 22. To shutoff the fuel being supplied to the
fuel-fired burner 20, the electronic controller 76 closes the fuel
enable valve 140 and ceases to generate control signals on the
signal line 136 thereby causing the fuel injector 132 to cease to
inject fuel into the mixing chamber 146. Once the fuel remaining in
the fuel line 148 is consumed by the burner 20, no additional fuel
enters the fuel inlet nozzle 54 of the burner 20. Similarly, to
shutoff the fuel being supplied to the fuel-fired burner 22, the
electronic controller 76 closes the fuel enable valve 140 and
ceases to generate control signals on the signal line 138 thereby
causing the fuel injector 134 to cease to inject fuel into the
mixing chamber 146. Once the fuel remaining in the fuel line 150 is
consumed by the burner 22, no additional fuel enters the fuel inlet
nozzle 54 of the burner 22.
[0172] In step 408, the electronic controller 76 maintains the
supply of combustion air and atomization air to the burners 20, 22,
and also maintains operation of the igniters 170, 172.
Specifically, in the case of shutdown of the fuel-fired burner 20,
even though fuel is no longer being supplied to the burner 20, the
electronic controller 76 continues to supply combustion air to the
burner 20 via the air line 58 and continues to supply atomization
air via the fuel line 148. The controller 76 continues to operate
the igniter 170 to continue spark generation within the combustion
chamber 34 of the burner 20. In the case of shutdown of the
fuel-fired burner 22, even though fuel is no longer being supplied
to the burner 22, the electronic controller 76 continues to supply
combustion air to the burner 22 via the air line 58 and continues
to supply atomization air via the fuel line 150. The controller 76
continues to operate the igniter 172 to continue spark generation
within the combustion chamber 34 of the burner 22. Such continued
air supply and spark generation ensures that any remaining fuel in
the system is combusted by the burner 20, 22 thereby reducing, if
not eliminating, the emission of unburned hydrocarbons.
[0173] The electronic controller 76 continues to supply combustion
air and atomization air and operate the igniters as described above
for a predetermined period of time. Such a period of time is shown
graphically with the arrow 424 in FIG. 16. Once this predetermined
period of time has elapsed, the control routine advances to step
410.
[0174] In step 410, the electronic controller 76 shuts off the flow
of combustion air to the fuel-fired burner 20, 22. Specifically,
the electronic controller 76 ceases operation of the motor 92
thereby ceasing operation of the air pump 90. Subsequent to
shutdown of the air pump 90, the electronic controller 76 continues
to supply atomization air and continues to operate the igniters as
described above for a predetermined period of time. Once this
predetermined period of time has elapsed, the control routine
advances to step 412.
[0175] In step 412, the electronic controller 76 shuts off the flow
of atomization air to the fuel-fired burner 20, 22. Specifically,
the electronic controller 76 closes the atomization air valve 156
thereby reducing the flow of air to the mixing chamber 146 and
hence the burners 20, 22. Note that the cleaning air valve 154
remains open, and, as a result, a reduced flow of cleaning air
continues to be advanced into the mixing chamber 146 and, as a
result, supplied to the fuel-fired burners 20, 22. As described
above, the flow of cleaning air from the cleaning air valve 154 is
generally constantly supplied to the mixing chamber 146 during
operation of the engine 80 of the truck 12 to prevent the
accumulation of debris (e.g., soot) in the fuel inlet nozzles 54 of
the fuel-fired burners 20, 22.
[0176] In step 412, the electronic controller 76 ceases spark
generation within the combustion chamber 34 of the fuel-fired
burner 20, 22. Specifically, the electronic controller 76 ceases
operation of the igniter 170 (in the case of the burner 20) or the
igniter 172 (in the case of the burner 172) thereby causing the
spark to cease to be generated across the electrode gap 52 of the
electrodes 48, 50 of the burner 20, 22. The control routine 400
then ends.
[0177] As described above, during execution of the shutdown control
routine 400 (along with other times as well), there are occasions
in which the electronic controller 76 supplies combustion air to
one of the fuel-fired burners 20, 22, but does not supply fuel to
either burner 20, 22. As also described above, the motor 92 drives
both the fuel pump 122 and the air pump 90. Hence, when the motor
92 is driving the air pump 90 to supply combustion air, the fuel
pump 122 is also being driven. During the occasions in which
combustion air is being supplied a burner 20, 22, but fuel is not
being supplied to either burner 20, 22, fuel pumped by the fuel
pump 122 is returned to the truck's fuel tank 124 via the fuel
return line 142. As shown in FIG. 8, a fuel pressure sensor 426
senses fuel pressure in the fuel return line 142. Output from the
fuel pressure sensor 426 is communicated to the electronic
controller 76 via a signal line 428. If the fuel return line 142
becomes restricted such that fuel cannot readily flow back to the
tank 124, pressure on the seals of the fuel pump 122 may increase
thereby potentially necessitating repair or replacement of the pump
122.
[0178] As shown in FIG. 17, the electronic controller 76 executes a
control routine 450 to monitor the return fuel line 142. The
control routine 450 commences with step 452 in which the electronic
controller 76 determines the fuel pressure in the fuel return line
142. Specifically, the electronic controller 76 scans or reads the
signal line 428 to obtain the output from the fuel pressure sensor
426. The control routine 450 then advances to step 454.
[0179] In step 454, the electronic controller 76 determines if the
sensed fuel pressure is above a predetermined upper pressure limit.
If the fuel pressure is below the upper pressure limit, the control
routine 450 loops back to step 452 to continue monitoring output
from the fuel pressure sensor 426. However, if the fuel pressure is
above the upper control limit, the control routine 450 advances to
step 456.
[0180] In step 456, the electronic controller 76 shuts down
components associated with the control unit 18. In particular,
since the electronic controller 76 concluded in step 454 that fuel
pressure in the fuel return line 142 was above the upper control
limit, the controller 76, amongst other things, ceases operation of
the drive motor 92 thereby ceasing operation of the fuel pump 122.
The control routine 450 then advances to step 458.
[0181] In step 458, the electronic controller 76 generates an error
signal. For example, the electronic controller 76 may generate an
output signal which causes a visual, audible, or other type of
alarm to be generated for presentation to the operator (e.g., the
driver of the truck 12). Alternatively, the error signal may simply
cause an electronic log or the like to be updated with information
associated with the fuel pressure analysis of steps 452-456. It
should be appreciated that the error signal generated in step 458
may be configured for use with any type of alarming or error
tracking arrangement to fit the needs of a given system design.
Moreover, if the electronic controller 76 is so equipped, the error
signal (or a subsequent signal generated in response the error
signal) may be communicated to the engine control unit 78 via the
CAN interface 314. Armed with this information, the engine control
unit 78 may be programmed to perform additional analysis, generate
an error signal to the truck operator (e.g., an indicator light on
the truck's instrument cluster) indicating that the control unit 18
has shutdown, or store the error message in an error log which can
be accessed by a service technician. The control routine 450 then
ends.
[0182] Referring back to FIG. 8, the control unit 18 may be
equipped with a one or more sensors for detecting the presence of
predetermined environmental conditions within the interior chamber
112 of the control housing 72. For example, the control unit 18 may
be configured to include a smoke detector 460. Output from the
smoke detector 460 is communicated to the electronic controller 76
via a signal line 462. As will herein be described in greater
detail, the smoke detector 460 may be used to detect the presence
of fuel particles or smoke in the interior chamber 112 of the
control housing 72. If the presence of fuel particles or smoke is
detected, the system may be shutdown and an error signal generated.
The smoke detector 460 may be embodied as any type of smoke
detector. In the exemplary embodiment of the control unit 18
described herein, the smoke detector 460 is embodied as a
non-ionizing smoke detector such as a commercially available
IR-detector.
[0183] As shown in FIG. 18, the electronic controller 76 executes a
control routine 500 to monitor for the presence of fuel particles
or smoke in the interior chamber 112 of the control housing 72. The
control routine 500 commences with step 502 in which the electronic
controller 76 scans or reads the signal line 462 to obtain the
output from the smoke detector 460. Once the controller 76 has
obtained the output from the smoke detector 460, the control
routine 500 then advances to step 504.
[0184] In step 504, the electronic controller 76 determines if the
output from the smoke detector 460 is indicative of the presence of
fuel particles or smoke in the interior chamber 112 of the control
housing 72. If the output from the smoke detector 460 is not
indicative of the presence of fuel particles or smoke in the
interior chamber 112 of the control housing 72, the control routine
500 loops back to step 502 to continue monitoring output from the
detector 460. However, if the output from the smoke detector 460 is
indicative of the presence of fuel particles or smoke in the
interior chamber 112 of the control housing 72, a control signal is
generated, and the control routine 500 advances to step 506.
[0185] In step 506, the electronic controller 76 shuts down
components associated with the control unit 18. In particular,
since the electronic controller 76 concluded in step 454 that the
output of the smoke detector is indicative of the presence of fuel
particles or smoke in the interior chamber 112 of the control
housing 72, the controller 76, amongst other things, ceases
operation of the drive motor 92 thereby ceasing operation of the
fuel pump 122 and the air pump 90. The control routine 500 then
advances to step 508.
[0186] In step 508, the electronic controller 76 generates an error
signal. For example, the electronic controller 76 may generate an
output signal which causes a visual, audible, or other type of
alarm to be generated for presentation to the operator (e.g., the
driver of the truck 12). Alternatively, the error signal may simply
cause an electronic log or the like to be updated with information
associated with the analysis of steps 502 and 504. It should be
appreciated that the error signal generated in step 508 may be
configured for use with any type of alarming or error tracking
arrangement to fit the needs of a given system design. Moreover, if
the electronic controller 76 is so equipped, the error signal (or a
subsequent signal generated in response the error signal) may be
communicated to the engine control unit 78 via the CAN interface
314. Armed with this information, the engine control unit 78 may be
programmed to perform additional analysis, generate an error signal
to the truck operator (e.g., an indicator light on the truck's
instrument cluster) indicating that the control unit 18 has
shutdown, or store the error message in an error log which can be
accessed by a service technician. The control routine 500 then
ends.
[0187] As shown in FIG. 8, the control unit 18 may be configured
with other types of sensors for detecting the presence of
predetermined environmental conditions within the interior chamber
112 of the control housing 72. For example, the control unit 18 may
be configured to include a temperature sensor 510. Output from the
temperature sensor 510 is communicated to the electronic controller
76 via a signal line 512. As will herein be described in greater
detail, the temperature sensor 510 may be used to monitor the
temperature within the interior chamber 112 of the control housing
72. If the temperature within the interior chamber 112 of the
control housing 72 exceeds a predetermined upper temperature limit
(e.g., 125.degree. C.), the system may be shutdown and an error
signal generated. The temperature sensor 510 may be embodied as any
type of electronic temperature sensor. In the exemplary embodiment
of the control unit 18 described herein, the temperature sensor 510
is embodied as a commercially available thermocouple.
[0188] As shown in FIG. 19, the electronic controller 76 executes a
control routine 550 to monitor the temperature within the interior
chamber 112 of the control housing 72. The control routine 550
commences with step 552 in which the electronic controller 76 scans
or reads the signal line 512 to obtain the output from the
temperature sensor 510. Once the controller 76 has obtained the
output from the temperature sensor 510, the control routine 550
then advances to step 554.
[0189] In step 554, the electronic controller 76 determines if the
sensed temperature within the interior chamber 112 of the control
housing 72 is above a predetermined upper temperature limit (e.g.,
125.degree. C.). If the temperature within the interior chamber 112
of the control housing 72 is below the upper temperature limit, the
control routine 550 loops back to step 552 to continue monitoring
output from the temperature sensor 510. However, if the temperature
within the interior chamber 112 of the control housing 72 is above
the upper control limit, a control signal is generated, and the
control routine 550 advances to step 556.
[0190] In step 556, the electronic controller 76 shuts down
components associated with the control unit 18. In particular,
since the electronic controller 76 concluded in step 554 that the
temperature within the interior chamber 112 of the control housing
72 is above the upper control limit, the controller 76, amongst
other things, ceases operation of the drive motor 92 thereby
ceasing operation of the fuel pump 122 and the air pump 90. The
control routine 550 then advances to step 558.
[0191] In step 558, the electronic controller 76 generates an error
signal. For example, the electronic controller 76 may generate an
output signal which causes a visual, audible, or other type of
alarm to be generated for presentation to the operator (e.g., the
driver of the truck 12). Alternatively, the error signal may simply
cause an electronic log or the like to be updated with information
associated with the temperature analysis of steps 552 and 554. It
should be appreciated that the error signal generated in step 558
may be configured for use with any type of alarming or error
tracking arrangement to fit the needs of a given system design.
Moreover, if the electronic controller 76 is so equipped, the error
signal (or a subsequent signal generated in response the error
signal) may be communicated to the engine control unit 78 via the
CAN interface 314. Armed with this information, the engine control
unit 78 may be programmed to perform additional analysis, generate
an error signal to the truck operator (e.g., an indicator light on
the truck's instrument cluster) indicating that the control unit 18
has shutdown, or store the error message in an error log which can
be accessed by a service technician. The control routine 550 then
ends.
[0192] Referring now to FIG. 20, there is shown an emission
abatement assembly 600. The emission abatement assembly 600
includes a number of common components with the emission abatement
assembly 10. Common reference numerals are utilized to designate
common components between the two assemblies.
[0193] The emission abatement assembly 600 includes a controller
76, a fuel supply unit such as a fuel pump 122 under the control of
the controller 76, and a fuel-fired burner 606. The assembly 600
may be installed in the truck 12 either horizontally, vertically,
or upside-down vertically. A diesel oxidation catalyst 608 may
optionally be positioned upstream of the filter substrate 60, as
shown in FIG. 20. The diesel oxidation catalyst 608 (or any other
type of oxidation catalyst) may be used to oxidize any unburned
hydrocarbons and carbon monoxide (CO) thereby generating additional
heat which is transferred downstream to the filter substrate 60.
Alternatively, as shown in FIG. 21, the emission abatement assembly
600 may be configured without the diesel oxidation catalyst
608.
[0194] As described above, the filter substrate 60 may be
impregnated with a catalytic material such as, for example, a
precious metal catalytic material. The catalytic material may be,
for example, embodied as platinum, rhodium, palladium, including
combinations thereof, along with any other similar catalytic
materials. Use of a catalytic material lowers the temperature
needed to ignite trapped soot particles.
[0195] Unlike the assembly 10, in the exemplary embodiment
described herein, the emission abatement assembly 600 does not
utilize supplemental air pumped from an air pump such as the air
pump 90. As such, the combustion process is supported by oxygen in
the exhaust gas.
[0196] The fuel-fired burner 606 is shown in greater detail in
FIGS. 22 and 23. Hot exhaust gas enters the housing 610 through an
exhaust gas inlet 612. Note that unlike the assembly 10 in which
the exhaust gas enters through an inlet 36 which is perpendicular
to the flow direction through the housing of the assembly, the
exhaust gas inlet 612 is substantially co-axial with the flow
direction of the housing 610. As such, the gas inlet 612 and a gas
outlet 614 of the housing 610 are arranged along the same general
axis (see FIGS. 20 and 21).
[0197] Exhaust gas entering the housing 610 is split into two
streams. The inner stream 616 enters a chamber 618, and then flows
into a combustion chamber 620 through a number of holes 622, 624.
The hole pattern of the holes 622, 624 is shown in FIGS. 24 and 25.
The hole pattern is configured such that exhaust gas flowing
through the holes 622 swirls inside the combustion chamber 620,
thus facilitating the mixing of the injected fuel, the exhaust gas,
and combustion gases. One or more rows of the holes 622 may be
utilized to generate a desired flow/swirl. As shown in FIGS. 24 and
25, an upstream wall 628 of the combustion chamber 620 may also
have a number of holes 626 defined therein to allow a portion of
the exhaust gas flow to enter the chamber 620 without being first
advanced through the chamber 618.
[0198] The ends of the electrodes 48, 50 are placed downstream of
the nozzle 54 to ignite the fuel in the presence of exhaust gas.
The exhaust gas contains between 4%-20% oxygen which facilitates
combustion of the fuel. The exhaust gas passing through holes 624
mixes with the hot combustion gas that may contain unburned fuel,
hydrocarbons, CO, and other combustible gas. In the presence of the
oxygen in the exhaust gas, these gases further combust. A flow of
exhaust gas flows through a number of holes 630 thereby bypassing
the fuel-fired burner 606. This bypass flow of exhaust gas supplies
additional oxygen for the combustion of the combustion gas exiting
the combustion chamber 620.
[0199] A flame holder 632 is placed downstream of the combustion
zone to prevent the flame from reaching the diesel oxidation
catalyst 608 (or the filter substrate 60 in configurations without
a diesel oxidation catalyst such as shown in FIG. 21). A gas
distributor 634 may be positioned downstream of the combustion zone
to facilitate the mixing of the hot combustion gas and the exhaust
gas bypassing the fuel-fired burner 606, thus enhancing the
temperature distribution across the inlet of diesel oxidation
catalyst 608 and/or filter substrate 60. The distributor 634 may be
positioned around a portion of the walls of the combustion chamber
620 as shown in FIG. 22. An exemplary design of a gas distributor
634 that may be positioned in such a manner is shown in FIG. 26.
Alternatively, as shown in FIG. 27, the gas distributor 634 may be
positioned downstream of the outlet of the combustion chamber 620.
An exemplary design of a gas distributor 634 that may be positioned
in such a manner is shown in FIG. 28.
[0200] Referring now to FIG. 27, another exemplary design of the
fuel-fired burner is shown in greater detail. In this embodiment,
some exhaust gas flows through the holes 622 whose hole pattern is
similar to the hole pattern shown in FIG. 24, thereby creating gas
swirl inside the combustion chamber. The hot flame which contains
unburned fuel, hydrocarbons, CO, and other combustible gas burns
further downstream in the assembly of FIG. 27 relative to the
assembly of FIG. 22.
[0201] As shown in FIG. 27, an additional flame holder 636 may be
positioned between the flame holder 632 and the fuel-fired burner
606. As shown in solid lines, the flame holder 636 may be designed
in a concave configuration or, as shown in phantom lines, a convex
configuration.
[0202] Other variations of the exemplary designs of the emission
abatement assemblies described herein are also contemplated. For
example, as described above, the air pump 90 may be embodied as any
type of air pump including a relatively high flow/high efficiency
air pump. A variable air flow pump that increases output at high
engine load conditions may also be used. Alternatively, a variable
air flow pump that only operates at high engine load conditions may
be used. The pump 90 may be embodied as a centrifugal compressor or
a roots blower.
[0203] The size of the combustion chamber 34, 620 may also be
varied to fit the needs of a given system design. For example, a
relatively large (16" diameter) combustion chamber 34, 620 may be
used to slow exhaust gas velocity thereby enhancing combustion
efficiency of the fuel-fired burners. Relatively smooth/efficient
air flow configurations, such as the "axial" configurations shown
in FIGS. 20 and 21, may also be used to enhance the flow
characteristics of a given design.
[0204] The manner in which fuel is injected into the fuel-fired
burners 20, 22, 606 may also be varied, if desired. For example, a
staged fuel injection arrangement may be used in which a first
amount of fuel is injected into the burner to create an initial
flame. The initial flame is then used to ignite a second amount of
injected fuel.
[0205] A modulated fuel flow arrangement could also be utilized to
increase the surface area of the fuel spray. For example, a
dithering fuel average may be used in which the amount of injected
fuel is dithered around a desired average fuel amount. For
instance, the injected fuel rate may be dithered between 25% and
75% to produce an average fuel rate of 50%.
[0206] Operation of the engine 80, and its associated components,
may also be controlled to facilitate operation of the emission
abatement assemblies described herein. For example, in the case of
operation of an emission abatement assembly that does not utilize
supplemental air (e.g., the assemblies of FIGS. 20 and 21), the
position of the EGR valve of the engine 80 may be coordinated with
regeneration of the particulate filter. For instance, to increase
both the temperature and the oxygen content in the exhaust gas, the
engine's EGR valve may be momentarily closed. It is estimated that
filter regeneration may require about ten minutes of time. During
such a brief period of time, the EGR valve may be closed. In such a
case, filter regeneration may be coordinated with engine idle
conditions.
[0207] In other embodiments, the engine 80 may be controlled such
the EGR level is actually increased during filter regeneration. In
such a case, a fuel or fuel additive such as hydrogen gas may be
utilized to stabilize the flame of the fuel-fired burner. Hydrogen
gas may be supplied by either a storage tank or an onboard fuel
reformer.
[0208] Along a similar line, operation of the engine 80, and its
associated components, may be monitored to facilitate operation of
the emission abatement assemblies described herein. For example, in
the case of operation of an emission abatement assembly that does
not utilize supplemental air (i.e., an airless burner such as the
assemblies of FIGS. 20 and 21), operation of the engine may be
monitored so that, for example, filter regeneration occurs at
desired, predetermined engine operating conditions. For example, in
the case of an emission abatement assembly that does not utilize
supplemental air (e.g., the assemblies of FIGS. 20 and 21), it is
desirable to perform filter regeneration in the presence of exhaust
gas which contains a relatively high oxygen concentration. Such is
generally the case when the engine 80 is under relatively low load
conditions such as when the engine 80 is operating at idle or near
idle conditions (e.g., 600-1,000 RPM depending on the engine).
[0209] As will herein be described in more detail below, there are
a number of ways to determine when desirable, predetermined engine
conditions exist for filter regeneration of an emission abatement
assembly that does not utilize supplemental air. For example, a
predetermined engine speed range may be utilized in which case
filter regeneration is only performed if the engine is operating
within a predetermined range of engine speed. In such a case, the
controller 76 may monitor output from an engine speed sensor 890
(see FIG. 8) or the like to determine engine speed. It should be
appreciated that the controller may communicate with the engine
speed sensor 890 directly, or may obtain the output from the sensor
890 from the engine control unit 78 via the CAN interface 314.
[0210] Moreover, a predetermined engine load range may be utilized
to determine when desirable, predetermined engine conditions exist
for filter regeneration of an emission abatement assembly that does
not utilize supplemental air. In such a case, filter regeneration
is only performed if the engine is operating within the
predetermined range of engine load. To do so, the controller 76 may
first sense or otherwise determine certain engine parameters (e.g.,
RPM, turbo boost, etcetera) and then query or otherwise access a
preprogrammed engine load map to determine the load on the engine.
It should be appreciated that the controller 76 may be
preprogrammed with such an engine load map, or may obtain the
engine load from an engine load map programmed in the engine
control unit 78 via the CAN interface 314.
[0211] In addition, exhaust mass flow from the engine 80 may be
used to determine when desirable, predetermined engine conditions
exist for filter regeneration of an emission abatement assembly
that does not utilize supplemental air. For example, a
predetermined exhaust mass flow range may be utilized in which case
filter regeneration is only performed if the engine is operating
within a predetermined range of exhaust mass flow. In such a case,
the controller 76 may monitor output from a mass flow sensor 892
(see FIG. 8), such as a hot wire mass flow sensor, to determine
exhaust mass flow. It should be appreciated that the controller 76
may communicate with the mass flow sensor 892 directly, or may
obtain the output from the sensor 892 from the engine control unit
78 via the CAN interface 314. Alternatively, exhaust mass flow may
be calculated by the controller 76 in a conventional manner by use
of engine operation parameters such as engine RPM, turbo boost
pressure, and intake manifold temperature (along with other known
parameters such as engine displacement). It should be appreciated
that the controller 76 itself may calculate the mass flow, or it
may obtain the calculated mass flow from the engine control unit 78
via the CAN interface 314.
[0212] Referring now to FIG. 33, there is shown a control routine
850 for controlling regeneration an emission abatement assembly
that does not utilize supplemental air (i.e., an airless emission
abatement assembly). The routine 850 begins with step 852 in which
the routine determines if a request to startup the airless
fuel-fired burner 20, 22 (i.e., a burner startup request) has been
executed. It should be appreciated that a burner startup request
may take many different forms including, for example, a startup
request generated by a software control routine in response to
sensed, timed, or otherwise determined indication that one of the
particulate filters 24, 26 is in need of regeneration. For example,
a sensor-based scheme, map-based scheme, or a timing-based scheme
may be utilized to generate a startup request. As such, in step
852, if the control routine 850 detects a burner startup request, a
control signal is generated and the routine 850 advances to step
854. If the control routine 850 does not detect a burner startup
request, the routine 850 loops back to step 852 to continue
monitoring for such a request.
[0213] In step 854, the controller 76 determines if the engine 80
is operating within predetermined engine conditions. For example,
if a predetermined engine speed range is being utilized, in which
case filter regeneration is only performed if the engine is
operating within a predetermined range of engine speed, the
controller 76 monitors output from the engine speed sensor 890 or
otherwise determines engine speed. Thereafter, the controller 76
determines if the speed of the engine is within the predetermined
speed range. Alternatively, if a predetermined engine load range is
being utilized, in which case filter regeneration is only performed
if the engine is operating within the predetermined range of engine
load, the controller 76 senses or otherwise determines certain
engine parameters (e.g., RPM, turbo boost, etcetera) and thereafter
queries or otherwise accesses a preprogrammed engine load map to
determine the load on the engine. Thereafter, the controller 76
determines if the load of the engine is within the predetermined
range of engine load. Moreover, if a predetermined exhaust mass
flow range is being utilized, in which case filter regeneration is
only performed if the engine is operating within a predetermined
range of exhaust mass flow, the controller 76 senses, calculates,
or otherwise determines exhaust mass flow from the engine.
Thereafter, the controller 76 determines if the exhaust mass flow
of the engine is within the predetermined range of exhaust mass
flow. Hence, in step 854, if the controller 76 determines that the
engine 80 is operating within predetermined engine conditions, the
control routine 850 advances to step 856. However, if the engine is
not operating within predetermined engine conditions, the control
routine 850 loops back to step 854 to continue monitoring the
engine to determine when it is operating within such
conditions.
[0214] In step 856, the controller 76 commences filter
regeneration. Specifically, the electronic controller 76 operates
the fuel-fired burner 20, 22 to regenerate the particulate filter
24, 26 in any of the numerous manners described herein. However, it
should be appreciated that the fuel-fired burner 20, 22 is operated
without the assistance of combustion air (i.e., without the use of
supplemental air supply such as from the air pump 90). As such,
oxygen present in the engine exhaust gas sustains combustion of the
fuel delivered to the fuel-fired burner 20, 22. Heat generated by
the combustion of the fuel regenerates the particulate filter 24,
26. Once filter regeneration is complete, the control routine 850
ends.
[0215] It should be appreciated that the control routine 850 may
also be used to regenerate filters with the assistance supplemental
air, if desired. It should also be appreciated that the control
routine 850 may be modified in a manner in which filter
regeneration occurs even in the absence of a startup request. For
example, the controller 76 may be configured to regenerate one or
both of the particulate filters 24, 26 when the engine 80 is
operating within predetermined engine conditions irrespective of
whether the filters 24, 26 are loaded to a predetermined limit. In
such a way, the controller 76 can take advantage of any time oxygen
rich conditions are present in the exhaust gas.
[0216] Referring now to FIG. 35, another exemplary embodiments of
an emission abatement assembly 800 is shown. The assembly 800
includes a nozzle 802 which extends into an exhaust conduit to
inject fuel into a flow of exhaust gas. The electrodes 48, 50 are
positioned in a substantially vertical arrangement (as viewed in
the orientation of the drawings).
[0217] A flame holder 636 may be positioned in a number of
different positions relative to the electrodes 48, 50. For example,
as shown in FIG. 35, the flame holder 636 may be positioned
downstream of the nozzle 802, but upstream of the electrodes 48,
50. Alternatively, the flame holder 636 may be positioned
downstream of both the nozzle 802 and the electrodes 48, 50.
Moreover, the flame holder 632 may be designed in a concave
configuration (as shown in FIG. 35), or a convex configuration (not
shown).
[0218] A flow diffuser 644 may be positioned upstream of the diesel
oxidation catalyst 608 and/or the filter substrate 60 to facilitate
the mixing of the hot combustion gas from combustion zone proximate
to the nozzle 802 and the remaining exhaust gas, thus enhancing the
temperature distribution across the inlet of diesel oxidation
catalyst 608 and/or filter substrate 60. The flow diffuser 644 may
be embodied as any type of flow diffuser. In an exemplary
embodiment, the flow diffuser 644 may be embodied as the any of the
flow distributors 634 described above.
[0219] Referring now to FIG. 36, there is shown another exemplary
embodiment of the fuel-fired burner 20, 22. The embodiment shown in
FIG. 36 is similar to the embodiments previously described, with
the same reference numerals being used to designate similar
components. The fuel-fired burner 20, 22 has been modified to
reduce the exhaust gas flow through the combustion chamber 34. It
has been found that such a modification reduces (perhaps
significantly) hydrocarbon and CO slip, while also reducing other
emissions.
[0220] In essence, the flow of exhaust gas entering through the
exhaust gas inlet port 36 is separated into two flows, one of which
is advanced through the combustion chamber 34 (i.e., a combustion
flow), the other of which bypasses the combustion chamber 34 (i.e.,
a bypass flow). As such, exhaust gas flow through the combustion
chamber 34 of the fuel-fired burner 20, 22 of FIG. 36 is reduced
relative to the burner of, for example, FIG. 5. As a result, the
percentage of the exhaust gas flow bypassing the combustion chamber
34 (i.e., advancing through the openings 42 of the shroud 44) is
increased relative to the design of FIG. 5.
[0221] As will herein be described in greater detail, the design of
the combustion chamber 34 may be altered to provide control of the
exhaust gas flowing therethrough (i.e., control the velocity and
direction of exhaust gas flow through the combustion chamber).
Moreover, components such as diverter plates may also be used to
control the exhaust gas flow in such a manner.
[0222] One exemplary manner of controlling the exhaust gas flow
through the fuel-fired burner 20, 22 in such a manner is shown in
FIG. 36. In this case, the combustion chamber 34 includes a
generally annular shaped outer wall 902 having two wall halves 904,
906. The first wall half 904 faces away from the exhaust gas inlet
port 36, whereas the second wall half 906 faces toward the exhaust
gas inlet port 36. As shown in FIG. 36, the first wall half 904 has
a number of the gas inlet openings 40 defined therein. The
collective surface areas of the gas inlet openings 40 of the first
wall half 904 define a first void area, whereas the collective
surface areas of the gas inlet openings of the second wall half 906
define a second void area. The second void area of the second wall
half 904 is less than the first void area of the first wall half.
As such, a reduced portion of the exhaust gas entering the
fuel-fired burner 20, 22 through the exhaust gas inlet 36 flows
into the combustion chamber 34 relative to, for example, the design
of the fuel-fired burner of FIG. 5. As a result, the magnitude of
the combustion flow (i.e., the flow of exhaust gas entering the
combustion chamber 34) is reduced relative to the design of FIG. 5.
It should be appreciated that such a configuration not only reduces
the magnitude of the exhaust gas entering the combustion chamber
34, but also reduces the velocity of the exhaust gas entering the
combustion chamber 34 (relative to, for example, the design of FIG.
5). Moreover, such a configuration also reduces the flow of exhaust
gas entering the fuel-fired burner 20, 22 through the exhaust gas
inlet 36 that flows directly into the combustion chamber 34 (i.e.,
through the wall half 906), and, as a result, is impinged upon the
flame generated therein.
[0223] Referring now to FIG. 37, there is shown another embodiment
of the fuel-fired burner 20, 22 in which the second wall half 906
of the combustion chamber 34 is substantially devoid of the gas
inlet openings 40. For example, the collective surface areas of the
gas inlet openings of the second wall half 906 define a void area
of zero. As a result, exhaust gas entering the fuel-fired burner
20, 22 through the exhaust gas inlet port 36 does not flow directly
into the combustion chamber 34, and, as a result, is not impinged
upon the flame generated therein. Rather, the combustion flow of
exhaust gas enters the combustion chamber 34 through the gas inlet
openings 40 formed in the first wall half 904 of the combustion
chamber 34 (i.e., the surfaces that do not face the exhaust gas
inlet 36). The balance of the flow of exhaust gas entering the
exhaust gas inlet port 36 bypasses the combustion chamber 34.
[0224] It should be appreciated that the size and location of the
gas inlet openings 40 on either wall half 904, 906 may be
configured to generate any desired flow characteristics within the
combustion chamber 34 (e.g., velocity and direction).
[0225] Although the proportions of the separated flows (i.e., the
combustion flow and the bypass flow) are described as being a
function of the gas inlet openings 40 formed in the outer wall 902
of the combustion chamber 34, the exhaust gas flow entering the
exhaust gas inlet port 36 may be separated in other ways. For
example, a plate or "patch" may be secured to the combustion
chamber 34 to block any number of gas inlet openings 40 that may
already exist in the chamber 34. An example of such a plate 912 is
shown in FIG. 44. The plate 912 may be positioned around the outer
wall 902 of the combustion chamber 34 of the burner design shown
in, for example, FIG. 5. The seam 918 created when the two ends 914
of the plate 912 are secured together faces the exhaust gas inlet
port 36. As shown in FIG. 45, when the plate 912 is installed in
such a manner, the exhaust gas flow entering the exhaust gas inlet
port 36 is impinged upon an area of the plate 912 (shown generally
as the shaded area 916) which is devoid of holes thereby preventing
the exhaust gas flow from being impinged directly on the flame
within the combustion chamber 34.
[0226] By controlling the flow of exhaust gas through the
combustion chamber 34 stability of the flame generated by the
fuel-fired burner 20, 22 may be enhanced. Indeed, it has been found
that when the velocity of the flame is greater than the velocity of
the exhaust gas moving through the chamber 34, a stable flame may
be more readily maintained. To the contrary, when the velocity of
the exhaust gas moving through the chamber 34 is greater than the
flame velocity, instability of the flame may occur.
[0227] As alluded to above, the size, number, and location of the
gas inlet openings 40 may be predetermined to produce a desired
flow through the combustion chamber. In an exemplary embodiment,
the fuel-fired burner 20, 22 is configured such that about 70% of
the exhaust gas entering through the inlet 36 is advanced through
the combustion chamber 34 (with the balance of the exhaust gas
bypassing the chamber 34). In another exemplary embodiment, the
fuel-fired burner 20, 22 is configured such that about 50%-70% of
the exhaust gas entering through the inlet 36 is advanced through
the combustion chamber 34 (with the balance of the exhaust gas
bypassing the chamber 34). In yet another exemplary embodiment, the
fuel-fired burner 20, 22 is configured such that less than 50% of
the exhaust gas entering through the inlet 36 is advanced through
the combustion chamber 34 (with the balance of the exhaust gas
bypassing the chamber 34). Flows other than these exemplary flow
arrangements are contemplated.
[0228] As alluded to above, in lieu of, or in addition to, removal
of the gas inlet openings 40 from the outer wall 902 of the
combustion chamber 34, the exhaust gas flow entering the gas inlet
port 36 may be separated into a desired combustion flow and bypass
flow in numerous different ways. For example, a number of diverter
plates may be used to direct a desired amount of exhaust gas flow
through the combustion chamber 34 while directing the balance of
the flow to bypass the chamber. Examples of such plates 910 are
shown in FIGS. 38-43, although other configurations are
contemplated. It should be appreciated that such plates 910 may be
configured to direct the desired portion of the flow through the
combustion chamber 34 while also preventing an increase in
backpressure within the exhaust system.
[0229] The size, shape, and/or location of the openings 42 defined
in the bypass shroud 44 may also be altered to generate desired
flow characteristics. For example, the size, shape, and/or location
of the openings 42 may be configured to accommodate for "hot spots"
or "cool spots" on the upstream face of the filter substrate 60.
Indeed, thermal analysis may be performed on the filter substrate
60 to determine where such hot spots or cool spots exist. The size,
shape, and/or location of the openings 42 defined in the bypass
shroud 44 may then be altered based on such an analysis.
[0230] For example, the size of the openings 42 upstream (relative
to exhaust gas flow) of a cool spot may be reduced. This increases
the temperature on the cool spot during filter regeneration by
reducing the amount of exhaust gas flowing through the cool
spot.
[0231] Conversely, the size of the openings 42 upstream (relative
to exhaust gas flow) of a hot spot may be increased. This decreases
the temperature on the hot spot during filter regeneration by
increasing the amount of exhaust gas flowing through the hot
spot.
[0232] As a result, it is contemplated to construct a bypass shroud
44 that includes a number of different sized openings 42 to
accommodate varying surface temperatures on the upstream surface of
the filter substrate 60.
[0233] While the disclosure is susceptible to various modifications
and alternative forms, specific exemplary embodiments thereof have
been shown by way of example in the drawings and has herein be
described in detail. It should be understood, however, that there
is no intent to limit the disclosure to the particular forms
disclosed, but on the contrary, the intention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the disclosure.
[0234] There are a plurality of advantages of the present
disclosure arising from the various features of the apparatus,
systems, and methods described herein. It will be noted that
alternative embodiments of the apparatus, systems, and methods of
the present disclosure may not include all of the features
described yet still benefit from at least some of the advantages of
such features. Those of ordinary skill in the art may readily
devise their own implementations of apparatus, systems, and methods
that incorporate one or more of the features of the present
disclosure and fall within the spirit and scope of the present
disclosure.
[0235] For example, it should be appreciated that the order of many
of the steps of the control routines described herein may be
altered. Moreover, many steps of the control routines may be
performed in parallel with one another.
* * * * *