U.S. patent application number 12/014603 was filed with the patent office on 2009-07-16 for method and apparatus for regenerating a particulate filter of an emission abatement assembly.
Invention is credited to Christopher R. Huffmeyer.
Application Number | 20090178395 12/014603 |
Document ID | / |
Family ID | 40849476 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090178395 |
Kind Code |
A1 |
Huffmeyer; Christopher R. |
July 16, 2009 |
Method and Apparatus for Regenerating a Particulate Filter of an
Emission Abatement Assembly
Abstract
A method of operating an emission abatement assembly includes
supplying a first flow rate of fuel to a fuel-fired burner to
generate heat to combust soot trapped in a particulate filter. The
method further includes supplying a second flow rate of fuel to the
burner in an attempt to increase the temperature of the heat with
the second flow rate of fuel being greater than the first flow rate
of fuel. The method further includes determining the temperature of
the heat. The method further includes supplying a third flow rate
of fuel to the burner if the temperature of the heat decreases in
response to supplying the second flow rate of fuel with the third
flow rate of fuel being less than the second flow rate of fuel. An
associated emission abatement assembly is also disclosed.
Inventors: |
Huffmeyer; Christopher R.;
(Columbus, IN) |
Correspondence
Address: |
BARNES & THORNBURG LLP
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Family ID: |
40849476 |
Appl. No.: |
12/014603 |
Filed: |
January 15, 2008 |
Current U.S.
Class: |
60/297 ;
60/303 |
Current CPC
Class: |
F01N 3/2066 20130101;
F01N 2240/14 20130101; Y02T 10/12 20130101; F01N 2560/06 20130101;
F01N 2900/1404 20130101; Y02T 10/47 20130101; F01N 9/00 20130101;
F01N 2590/08 20130101; F01N 2900/0408 20130101; F01N 3/025
20130101; F01N 3/2033 20130101; F01N 2900/0601 20130101; Y02T 10/24
20130101; Y02T 10/26 20130101; Y02T 10/40 20130101; F01N 2900/0418
20130101 |
Class at
Publication: |
60/297 ;
60/303 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Claims
1. A method of operating an emission abatement assembly, the method
comprising: supplying a first flow rate of fuel to a fuel-fired
burner to generate heat to combust soot trapped in a particulate
filter, supplying a second flow rate of fuel to the burner in an
attempt to increase the temperature of the heat, the second flow
rate of fuel being greater than the first flow rate of fuel,
determining the temperature of the heat, and supplying a third flow
rate of fuel to the burner if the temperature of the heat decreases
in response to supplying the second flow rate of fuel, the third
flow rate of fuel being less than the second flow rate of fuel.
2. The method of claim 1, wherein: determining the temperature of
the heat comprises determining the temperature of the heat at an
inlet of the particulate filter, and supplying the third flow rate
of fuel comprises supplying the third flow rate of fuel to the
burner if the temperature of the heat at the inlet of the
particulate filter decreases in response to supplying the second
flow rate of fuel.
3. The method of claim 1, wherein determining the temperature of
the heat comprises determining the temperature of the heat with a
temperature sensor.
4. The method of claim 1, wherein determining the temperature of
the heat comprises determining the temperature of the heat over a
predetermined period of time.
5. The method of claim 4, wherein, determining the temperature of
the heat comprises: (i) sampling the temperature of the heat for a
plurality of samples over the predetermined amount of time to
obtain a plurality of samples, and (ii) determining a temperature
trend based upon the plurality samples.
6. The method of claim 5, wherein supplying the third flow rate of
fuel comprises supplying the third flow rate of fuel to the burner
if the temperature trend indicates that the temperature of the heat
is decreasing.
7. An emission abatement assembly, comprising: a particulate
filter, a fuel-fired burner positioned upstream of the particulate
filter, the fuel-fired burner being configured to generate heat to
combust soot trapped in the particulate filter, a temperature
sensor configured to generate a signal indicative of the heat
generated by the burner, an electronically-controlled fuel delivery
assembly operable to deliver fuel to the fuel-fired burner, and a
controller electrically coupled to the fuel delivery assembly, 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: operate the fuel delivery
assembly to supply a first flow rate fuel to the burner to generate
heat to combust soot trapped in a particulate filter, operate the
fuel delivery assembly to supply a second flow rate of fuel to the
burner in an attempt to increase the temperature of the heat, the
second flow rate of fuel being greater than the first flow rate of
fuel, determine the temperature of the heat based upon the signal
generated by the temperature sensor, and operate the fuel delivery
assembly to supply a third flow rate of fuel to the burner if the
temperature of the heat decreases in response to supplying the
second flow rate of fuel, the third flow rate of fuel being less
than the second flow rate of fuel.
8. The emission abatement assembly of claim 7, wherein the
temperature sensor is positioned at an inlet of the particulate
filter, the temperature sensor configured to generate a signal
indicating the temperature of the heat at the inlet of the
particulate filter.
9. The emission abatement assembly of claim 8, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to determine the temperature of the heat at the
inlet of the filter based upon the signal generated by the
temperature sensor.
10. The emission abatement assembly of claim 9, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to operate the fuel delivery assembly to supply
the third flow rate of fuel to the burner if the temperature of the
heat at the inlet of the filter decreases in response to supplying
the second flow rate of fuel.
11. The emission abatement assembly of claim 7, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to: sample the temperature of the heat based
upon the signal generated by the temperature sensor over a
predetermined amount of time to obtain a plurality of samples, and
determine the temperature of the heat based upon the plurality of
samples.
12. The emission abatement assembly of claim 8, wherein the
plurality of instructions, when executed by the processor, further
cause the processor to: determine a temperature trend based upon
the plurality of samples, and operate the fuel delivery system to
supply the third rate of fuel to the burner if the temperature
trend indicates that the temperature of the heat decreases in
response to the supplying the second flow rate of fuel.
Description
CROSS REFERENCE
[0001] Cross reference is made to copending U.S. patent
applications Ser. No. ______ entitled "METHOD AND APPARATUS FOR
CONTROLLING A FUEL-FIRED BURNER OF AN EMISSION ABATEMENT ASSEMBLY"
by Samuel N. Crane Jr. (Attorney Docket No. 44950-203708,
07ARM0134); Ser. No. ______ entitled "METHOD AND APPARATUS FOR
CLEANING THE ELECTRODES OF A FUEL-FIRED BURNER OF AN EMISSION
ABATEMENT ASSEMBLY" by Samuel N. Crane Jr. (Attorney Docket No.
44950-203709, 07ARM0149); Ser. No. ______ entitled "METHOD AND
APPARATUS FOR OPERATING AN EMISSION ABATEMENT ASSEMBLY" by Tony R.
Parrish (Attorney Docket No. 44950-203711, 07ARM0146); and Ser. No.
______ entitled "APPARATUS FOR DIRECTING EXHAUST FLOW THROUGH A
FUEL-FIRED BURNER OF AN EMISSION ABATEMENT ASSEMBLY" by John P.
Nohl and Samuel N. Crane Jr. (Attorney Docket No. 44950-203712,
07ARM0132).
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to diesel emission
abatement devices.
BACKGROUND
[0003] Untreated internal combustion engine emissions (e.g., diesel
emissions) include various effluents such as oxides of nitrogen
(NOx), 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.
[0004] 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.
[0005] Selective catalytic reduction (SCR) is used for NOx
reduction in internal combustion engine exhaust. The efficiency of
NOx reduction of an SCR catalyst is based upon the temperature of
exhaust gas being exposed thereto. Exhaust gas is typically at
low-efficiency temperatures during low-load conditions. Heat
sources have been used to raise the temperature of the exhaust gas
to a level allowing the SCR catalyst to perform more
efficiently.
SUMMARY
[0006] According to one aspect of the disclosure, a method of
operating an emission abatement assembly may include supplying a
first flow rate of fuel to a fuel-fired burner to generate heat to
combust soot trapped in a particulate filter. The method may
further include supplying a second flow rate of fuel to the burner
in an attempt to increase the temperature of the heat with the
second flow rate of fuel being greater than the first flow rate of
fuel. The method may further include determining the temperature of
the heat. The method may further include supplying a third flow
rate of fuel to the burner if the temperature of the heat decreases
in response to supplying the second flow rate of fuel with the
third flow rate of fuel being less than the second flow rate of
fuel.
[0007] According to another aspect of the disclosure, an emission
abatement assembly may include a particulate filter and a
fuel-fired burner positioned upstream of the particulate filter
with the fuel-fired burner being configured to generate heat to
combust soot trapped in the particulate filter. The emission
abatement assembly may further include a temperature sensor
configured to generate a signal indicative of the heat generated by
the burner and an electronically-controlled fuel delivery assembly
operable to deliver fuel to the fuel-fired burner. The emission
abatement assembly may further include a controller electrically
coupled to the fuel delivery assembly. The controller may include a
processor and a memory device electrically coupled to the
processor. The memory device may include stored therein a plurality
of instructions which, when executed by the processor, cause the
processor to operate the fuel delivery assembly to supply a first
flow rate fuel to the burner to generate heat to combust soot
trapped in a particulate filter. The processor may further be
caused to operate the fuel delivery assembly to supply a second
flow rate of fuel to the burner in an attempt to increase the
temperature of the heat with the second flow rate of fuel being
greater than the first flow rate of fuel. The processor may further
be caused to determine the temperature of the heat based upon the
signal generated by the temperature sensor. The processor may
further be caused to operate the fuel delivery assembly to supply a
third flow rate of fuel to the burner if the temperature of the
heat decreases in response to supplying the second flow rate of
fuel with the third flow rate of fuel being less than the second
flow rate of fuel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a rear elevational view of an on-highway truck
with an emission abatement assembly installed thereon;
[0009] FIG. 2 is a perspective view of an emission abatement
assembly;
[0010] FIG. 3 is an elevational view of the end of the emission
abatement assembly as viewed in the direction of the arrows of line
3-3 of FIG. 2;
[0011] FIG. 4 is a cross sectional view of the emission abatement
assembly of FIG. 2 taken along the line 4-4 of FIG. 3, as viewed in
the direction of the arrows, note that the filter housing and the
collector housing are not shown in cross section for clarity of
description;
[0012] FIG. 5 is an enlarged cross sectional view of the fuel-fired
burner of the emission abatement assembly of FIG. 4;
[0013] FIG. 6 is an enlarged cross sectional view of the mixing
baffle of the fuel-fired burner of FIGS. 2-5;
[0014] FIG. 7 is a diagrammatic internal top view of a fuel-fired
burner;
[0015] FIG. 8 is a diagrammatic internal top view of an alternative
fuel-fired burner;
[0016] FIG. 9 is a block diagram of an illustrative emission
abatement assembly;
[0017] FIG. 10 is a flowchart of a control routine for operating a
fuel-fired burner in an emission abatement assembly;
[0018] FIG. 11 is a flowchart of another control routine for
operating a fuel-fired burner in an emission abatement
assembly;
[0019] FIG. 12 is a flowchart of another control routine for
operating a fuel-fired burner in an emission abatement assembly;
and
[0020] FIG. 13 is a flowchart of another control routine for
operating a fuel-fired burner in an emission abatement
assembly.
DETAILED DESCRIPTION OF THE DRAWINGS
[0021] As will herein be described in more detail, FIG. 1
illustratively shows emission abatement assemblies 10, 12 for use
with an internal combustion engine, such as the diesel engine of an
on-highway truck 14. As illustratively shown in FIG. 1, each of the
emission abatement assemblies 10, 12 has a fuel-fired burner 16, 18
and a particulate filter 20, 22, respectively. The fuel-fired
burners 16, 18 are positioned upstream (relative to exhaust gas
flow from the engine) from the respective particulate filters 20,
22. During operation of the engine, exhaust gas flows through a
split exhaust gas inlet pipe 19 before entering the emission
abatement assemblies 10, 12, and thus the particulate filters 20,
22 thereby trapping soot in the filters. Treated exhaust gas is
released into the atmosphere through exhaust pipes 24, 26. From
time to time during operation of the engine, the fuel-fired burner
16 regenerates the particulate filter 20 and the fuel-fired burner
18 regenerates the particulate filter 22. Also shown in FIG. 1 are
fuel lines 37, 41 and air lines 39, 43 for the emission abatement
assemblies 10, 12, respectively.
[0022] Referring now to FIGS. 2-6, the emission abatement assembly
10 is shown in greater detail. It should be appreciated that the
emission abatement assembly 10 is substantially identical to the
emission abatement assembly 12. As such, the discussion relating to
the emission abatement assembly 10 of FIGS. 2-6 is relevant to the
emission abatement assembly 12.
[0023] As shown in FIGS. 4 and 5, the fuel-fired burner 16 includes
a housing 15 having a combustion chamber 17 positioned therein. The
exhaust gas inlet pipe 19 is illustratively shown in FIGS. 4 and 5
as being disposed through the housing 15 allowing the pipe 19 to
conduct exhaust gas from a diesel engine (not shown) into the
housing 15. The pipe 19 includes an elbow 23 disposed on an outlet
end positioned in the housing 15. The elbow 23 allows exhaust gas
flowing through the pipe 19 to be directed toward a wall 25 of the
housing 15 to impinge upon the wall 25 prior to reaching the
combustion chamber 17. FIG. 7 shows a diagrammatic internal top
view (with respect to the orientation shown in FIG. 1) of the
fuel-fired burner 16, which illustrates a manner in which the
exhaust gas flows into the housing 15 and impinges upon the wall
25. As indicated by the arrows, the exhaust gas, upon impinging the
wall 25, flows in a swirling pattern as the exhaust gas also flows
downstream (relative to exhaust gas flow) through the housing 15
towards the filter 20.
[0024] Again referring to FIGS. 4 and 5, the combustion chamber 17
includes a wall 45 circumscribing a space 47 where the flame of the
burner 16 is positioned. The wall 45 is open at its end proximate
to the filter 20 with the wall 45 including a number of gas inlet
openings 22 defined therein. The exhaust gas is permitted to flow
into the combustion chamber 17 through the inlet openings 22. In
such a way, a flame present inside the combustion chamber 17 is
protected from the full engine exhaust gas flow, while controlled
amounts of engine exhaust gas are permitted to enter the combustion
chamber 17 to provide oxygen to facilitate combustion of the fuel
supplied to the burner 12. Directing the exhaust gas through the
elbow 23 such that it is not exiting the pipe 19 directly toward
the combustion chamber 17 further protects the flame. As the
exhaust gas impinges upon the wall 25 and swirls through the
housing 15, the exhaust gas will diffuse such that a portion of it
enters the combustion chamber 17. The exhaust gas not entering the
combustion chamber 17 is directed through a number of openings 35
defined in a shroud 27.
[0025] The fuel-fired burner 16 also includes an electrode assembly
having a pair of electrodes 28, 30 as illustratively shown in FIGS.
3-5. When power is applied to the electrodes 28, 30, a spark is
generated in the gap 32 between the electrodes 28, 30. Fuel flows
from the fuel line 37 and enters the fuel-fired burner 16 through a
fuel inlet nozzle 34 and is advanced through the gap 32 between the
electrodes 28, 30 thereby causing the fuel to be ignited by the
spark generated by the electrodes 28, 30. It should be appreciated
that the fuel entering the nozzle 34 is generally in the form of a
controlled air/fuel mixture.
[0026] The fuel-fired burner 16 also includes a combustion air
inlet 36. An air pump, or other pressurized air source such as the
truck's turbocharger or air brake system, generates a flow of
pressurized air which is advanced to the combustion air inlet 36.
During regeneration of the particulate filter 20, a flow of air is
introduced into the fuel-fired burner 16 through the air line 39
and the combustion air inlet 36 to provide oxygen (in addition to
oxygen present in the exhaust gas) to sustain combustion of the
fuel.
[0027] As shown in FIG. 4, the particulate filter 20 is positioned
downstream from the outlet 40 of the housing 15 of the fuel-fired
burner 16. The particulate filter 20 includes a filter substrate
42. As shown in FIG. 4, the substrate 42 is positioned in a filter
housing 44. The filter housing 44 is secured to the burner housing
15. As such, gas exiting the burner housing 15 is directed into the
filter housing 44 and through the substrate 42. The particulate
filter 20 may be any type of commercially available particulate
filter. For example, the particulate filter 20 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 42 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.
[0028] The filter housing 44 is secured to a housing 46 of a
collector 48. Specifically, an outlet 50 of the filter housing 44
is secured to an inlet 52 of the collector housing 46. As such,
processed (i.e., filtered) exhaust gas exiting the filter substrate
42 (and hence the filter housing 44) is advanced into the collector
48. The processed exhaust gas is then advanced through a gas outlet
54. In FIG. 1, the gas outlet 54 is coupled to the exhaust pipe 24,
which conducts the processed exhaust gas into the atmosphere.
However, it should be appreciated that the gas outlet 54 may be
coupled to a subsequent emission abatement device (e.g., see FIG.
9) allowing further exhaust gas processing prior to the exhaust gas
being released into the atmosphere if the engine's exhaust system
is equipped with such a device.
[0029] Referring again to FIGS. 4-6, a mixing baffle 56 is
positioned in the burner housing 15. The mixing baffle 56 is
positioned between the shroud 27 and the outlet 40 of the burner
housing 15. In the illustrative embodiment described herein, the
mixing baffle 56 includes a domed diverter plate 58, a perforated
annular ring 60, and a collector plate 62. As shown in FIGS. 4 and
5, the collector plate 62 is welded or otherwise secured to the
inner surface of the burner housing 15. The collector plate 62 has
a hole 64 in the center thereof. The perforated annular ring 60 is
welded or otherwise secured to the collector plate 62. The inner
diameter of the annular ring 60 is larger than the diameter of the
hole 64. As such, the annular ring 60 surrounds the hole 64 of the
collector plate 62. The diverter plate 58 is welded or otherwise
secured to the end of the annular ring 60 opposite to the end that
is secured to the collector plate 62. The diverter plate 58 is
solid (i.e., it does not have holes or openings formed therein),
and, as such, functions to block the flow of exhaust gas linearly
through the mixing baffle 56. Instead, the diverter plate 58
diverts the flow of exhaust gas radially outwardly.
[0030] The mixing baffle 56 functions to mix the hot flow of
exhaust gas directed through the combustion chamber 17 and cold
flow of exhaust gas that bypasses the combustion chamber 17 during
filter regeneration thereby introducing a mixed flow of exhaust gas
into the particulate filter 20. In particular, as described above,
the flow of exhaust gas swirling in the combustion chamber housing
15 (see FIG. 7) is split into two flows--(i) a cold bypass flow
which bypasses the combustion chamber 17 and is advanced through
the openings 35 of the shroud 27 and, (ii) a hot combustion flow
which flows into the combustion chamber 17 where it is
significantly heated by the flame present therein. The mixing
baffle 56 forces both flows together through a narrow area and then
causes such a concentrated flow to then flow radially outwardly
thereby mixing the two flows together. To do so, the cold flow of
exhaust gas advances through the openings 35 in the shroud 27 and
thereafter is directed into contact with the upstream face 66 of
the collector plate 62. The shape of the collector plate 62 directs
the cold flow toward its hole 64.
[0031] Likewise, the hot flow of exhaust gas is directed toward the
hole of the collector plate 62. In particular, the hot flow of
exhaust gas is prevented from axially exiting the combustion
chamber 17 by a domed flame catch 68. The flame catch 68 forces the
hot flow of exhaust gas radially outwardly through a number of
openings 70 defined in a perforated annular ring 72, which is
similar to the perforated annular ring 62 of the mixing baffle 56.
The hot flow of exhaust gas is then directed toward the upstream
face 66 of the collector plate 62 by a combination of surfaces
including the downstream face 74 of the shroud 27 and the wall 25
of the burner housing 15. The hot flow of exhaust gas then contacts
the upstream face 66 of the collector plate where the shape of the
plate 62 causes the hot flow of exhaust gas to be directed toward
the hole 64. This begins the mixing of the hot flow of exhaust gas
with the cold flow of exhaust gas.
[0032] Mixing is continued as the cold and hot flows of exhaust gas
enter the hole 64 of the collector plate 62. The partially mixed
flow of gases is directed into contact with the diverter plate 58.
The diverter plate 58 blocks the linear flow of gases and directs
them outwardly in radial directions away from the diverter plate
58. The flow of exhaust gas is then directed through a number of
openings 76 formed in the perforated annular ring 62 of the mixing
baffle 56. This radial outward flow of exhaust gas impinges on the
inner surface of the burner housing 15 and is directed through the
outlet 40 of the burner housing 15 and into the inlet of the filter
housing 44 where the mixed flow of exhaust gas is utilized to
regenerate the filter substrate 42.
[0033] Hence, the elbow 23 causes the exhaust gas entering the
housing 15 to flow in a swirling manner while the exhaust gas flows
downstream through the housing 15 as the exhaust gas is split into
the bypass and combustion flow. The mixing baffle 56 forces the
mixing of the non-homogeneous exhaust gas flow through a narrow
area, and then causes the mixed flow to expand outwardly. Swirling
the exhaust gas entering the housing 15 and forcing it through the
mixing baffle 56, prevents the formation of a center flow or center
jet of hot gas from being impinged on the filter substrate 42. This
provides a more homogeneous mixture of the hot and cold flows
created prior to introduction of the combined flow onto the face of
the filter substrate thereby increasing filter regeneration
efficiency and reducing the potential for filter damage due to hot
spots. It should be appreciated that the elbow 23 and the mixing
baffle 56 may be implemented separately, or together, as described
herein.
[0034] FIG. 8 shows a diagrammatic internal top view of the
emission abatement assembly 10 implementing an alternative housing
15 and exhaust gas inlet pipe configuration 19. In this
illustrative configuration, the elbow 23 is eliminated and the pipe
19 is extended through an opening formed in the housing 15 such
that the exhaust gas flowing through the pipe 19 is directed along
the wall 25 upon entering the housing 15. This allows the exhaust
flow to impinge upon the wall 25 along its flow path, which induces
the flow of exhaust gas into a swirling pattern similar to that
induced with the configuration shown in FIG. 7. Similar to the
configuration shown in FIG. 7, the configuration of FIG. 8 may be
implemented with the mixing baffle 56.
[0035] Referring now to FIG. 9, there is illustratively shown a
diagrammatic view of an emission abatement assembly 90 used to
abate emissions generated by an internal combustion engine 92. The
emission abatement assembly 90 includes a fuel-fired burner 96
disposed downstream of the engine 92 along the exhaust path 94, the
engine 92 being a diesel engine in this illustrative embodiment.
The emission abatement assembly 90 further includes a diesel
oxidation catalyst (DOC) 98 positioned downstream of the burner 96
and a particulate filter 100 positioned downstream of the DOC 98
along the exhaust path 94. The emission abatement assembly 90
further includes a selective catalytic reduction (SCR) catalyst 102
positioned downstream of the filter 100. It should be appreciated
that the burner 96 and the filter 100 are substantially identical
to the burner 16 and the filter 20 previously described, thus names
and reference numerals of like components associated with the
burner 16 and the filter 20 previously described will be used in
regard to the description of the burner 96 and the filter 100.
[0036] Also shown in FIG. 9 is an electronic control unit (ECU) or
"electronic controller" 104. The electronic controller 104 is
typically positioned in a housing and located internally of the
truck 14 as previously discussed in regard to FIG. 1. The
electronic controller 104 is, in essence, the master computer
responsible for interpreting electrical signals sent by sensors
associated with the emission abatement assembly 90 (and in some
cases, the engine 92) and for activating electronically-controlled
components associated with the emission abatement assembly 90. For
example, the electronic controller 104 is operable to, amongst many
other things, determine when the particulate filter 100 of the
emission abatement assembly 90 is in need of regeneration,
calculate and control the amount and ratio of air and fuel to be
introduced into the fuel-fired burner 96, determine the temperature
in various locations within the emission abatement assembly 90,
operate numerous air and fuel valves, and communicate with an
engine control unit (not shown) associated with the engine 92 of
the truck 14. It should be appreciated that the electronic
controller 104 can also determine which emission abatement assembly
90 needs to be regenerated in a dual arrangement similar to that
described in regard to FIG. 1.
[0037] To carry out these tasks, the electronic controller 104
includes a number of electronic components commonly associated with
electronic units utilized in the control of electromechanical
systems. For example, the electronic controller 104 may include,
amongst other components customarily included in such devices, a
processor such as a microprocessor 106 and a memory device 108 such
as a programmable read-only memory device ("PROM") including
erasable PROM's (EPROM's or EEPRO's). The memory device 108 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 106, allows the electronic controller 104
to control operation of the emission abatement assembly 90.
[0038] The electronic controller 104 also includes an analog
interface circuit 110. The analog interface circuit 110 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 106. In particular, the analog
interface circuit 110, 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
processor 106. 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 106. It should also be
appreciated that if any one or more of the sensors associated with
the emission abatement assembly 90 generate a digital output
signal, the analog interface circuit 110 may be bypassed.
[0039] Similarly, the analog interface circuit 110 converts signals
from the microprocessor 106 into an output signal which is suitable
for presentation to the electrically-controlled components
associated with the emission abatement assembly 90 (e.g., the fuel
injectors, air valves, igniters, pump motor, etcetera). In
particular, the analog interface circuit 110, by use of a
digital-to-analog (D/A) converter (not shown) or the like, converts
the digital signals generated by the processor 106 into analog
signals for use by the electronically-controlled components
associated with the emission abatement assembly 90. 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 processor 106. It should
also be appreciated that if any one or more of the
electronically-controlled components associated with the emission
abatement assembly 90 operate on a digital input signal, the analog
interface circuit may be bypassed.
[0040] Hence, the electronic controller 104 may be operated to
control operation of the fuel-fired burner 96. In particular, the
electronic controller 104 executes a routine including, amongst
other things, a closed-loop control scheme in which the electronic
controller 104 monitors outputs of the sensors associated with the
emission abatement assembly 90 to control the inputs to the
electronically-controlled components associated therewith. To do
so, the electronic controller 104 communicates with the sensors
associated with the emission abatement assembly 90 to determine,
amongst numerous other things, the temperature at various locations
within the emission abatement assembly 90 and the pressure drop
across the filter substrate 42 of the filter 100. Armed with this
data, the electronic controller 104 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 28, 30 of the
burner 96, controlling the air advanced through a combustion air
inlet 36, etcetera.
[0041] It should be appreciated that the electronic controller 104
may communicate directly with the various sensors associated with
the emission abatement assembly 90, or may obtain the output from
the sensors from an engine control unit (not shown) associated with
the engine 92 via a controller area network (CAN) interface (not
shown), known to those of skill in the art. Alternatively, exhaust
mass flow may be calculated by the electronic controller 104 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 electronic controller 104 may itself
calculate the mass flow, or may obtain the calculated mass flow
from the engine control unit of the engine 92 via the CAN
interface.
[0042] As previously discussed, during operation of the engine 92,
the filter 100 eventually becomes full of soot from filtering the
exhaust gas generated by the engine 92 and needs to be regenerated
in order to continue filtering effectively. The processor 106 can
be programmed to control the burner 96 based upon predetermined
time intervals, event sensing, or other triggering occurrences
known to those in the art. Once the fuel-fired burner 96 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 100. The heat ignites and
burns soot particles trapped in the filter substrate 42 thereby
regenerating the particulate filter 100. 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.
[0043] The DOC 98 may be positioned upstream of the particulate
filter 100. The DOC 98 (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 100. An injector 97 may
optionally be implemented, shown in FIG. 9 as being positioned
upstream of the DOC 98, which is connected to the controller 104
through control line 101 and the fuel supply 117 through a fuel
line 103. This allows diesel fuel to be injected onto the DOC 98,
allowing the DOC 98 to catalyze a reaction between the injected
fuel and oxygen present in the exhaust gas flowing therethrough to
generate heat as well. Alternatively, the emission abatement
assembly 90 may be configured without the DOC 98.
[0044] In an illustrative embodiment, regeneration of the
particulate filter 100 may take only a few minutes. Moreover, it
should be appreciated that regeneration of the particulate filter
100 may be self-sustaining once initiated by heat from the burner
96, respectively. Specifically, once the filter 100 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 burner 96 may only be
required to commence the regeneration process of the filter 100
(i.e., begin the ignition process of the soot particles trapped
therein).
[0045] During its operation, the burner 96 receives an air/fuel
mixture, which can be controlled through control of a fuel injector
93 and the addition of combustion air through combustion air inlet
36 of the burner 96. As illustratively shown in FIG. 9, the burner
96 receives fuel from the fuel supply 117 through the fuel line
119. The burner 96 also receives oxygen for burning that is present
in the exhaust gas flowing therethrough. It is desirable to avoid
overfueling the burner 96, which occurs when more fuel is supplied
to the burner 96 than can be oxidized due to a lack of oxygen
available for complete oxidation. Furthermore, it is desirable to
supply an amount of fuel to the burner 96 such that the flame in
the combustion chamber is stable. In order to determine the proper
amount of fuel to supply in order to avoid overfueling and to
maintain flame stability, the amount of oxygen actually "useable"
by the burner 96 can be found.
[0046] Exhaust gas generated by the engine 92 typically contains
some amount of oxygen that can supplied downstream to the burner 96
during its operation. This amount can be theoretically determined
based upon mass flow calculations of the amount of air and fuel
being supplied to the engine 92. In other words, by calculating the
amount of air and fuel being supplied to the engine at a given
operating condition, the amount of residual air available in the
exhaust gas can be theoretically calculated. This theoretically
calculated value is typically referred to in the art as the amount
of "available oxygen" in the exhaust gas stream. However, in
reality, the entirety of this theoretical amount of available
oxygen in the exhaust gas is not truly usable for combustion by the
burner 96. This is true for a number of reasons. For example,
engine exhaust gas tends to be stratified, and in some cases highly
stratified. As a result, a significant amount of oxygen may be
trapped in a layer within a stratified flow thereby making it
unusable for combustion by the burner 96. Moreover, certain gases
present in the exhaust gas, such as CO and CO.sub.2, absorb a
portion of the heat being generated by the burner 96, thereby
extracting energy necessary for combustion. In the presence of such
instantaneous cool conditions, oxygen in the exhaust gas can go
unused. In short, for numerous different reasons, not all of the
oxygen present in the exhaust gas can be used for oxidation by the
burner 96.
[0047] Any fueling calculation that bases fueling of the burner 96
on the theoretical amount of available oxygen will generally result
in overfueling. As a result, the illustrative system and method
described herein bases fueling calculations on an
empirically-generated amount of usable oxygen in the exhaust gas.
Thus, for purposes of this disclosure, the term "useable oxygen"
means an empirically-generated amount of oxygen in the exhaust gas
of an engine that is produced at a given operating condition of the
engine that can actually be used by the burner of an emission
abatement assembly, with such an empirically-generated amount being
less than the theoretically-calculated amount of available oxygen
in the engine exhaust gas based on mass flow calculations of the
air and fuel being supplied to the engine at the same operating
condition of the engine. Fueling calculations based on the amount
of usable oxygen in the exhaust gas stream can be used to produce
air/fuel mixtures having desirable air-to-fuel ratios (e.g.,
stoichiometric) for operation of the burner 96 without the concern
for overfueling relative to similar fueling calculations based on
the theoretically-calculated amount of available oxygen in the
exhaust gas stream. Fueling calculations based on the amount of
usable oxygen in the exhaust gas stream can also be used to produce
more stable flames in the burner 96 relative to the calculations in
which the amount of oxygen in the exhaust gas stream is assumed to
be artificially low to avoid overfueling.
[0048] During operation of the burner 96, the amount of useable
oxygen present in the exhaust gas may not be sufficient to allow
the burner 96 to generate enough heat to regenerate the particulate
filter 100. However, supplemental oxygen from the air supply 112
can be supplied to the burner 96 in a similar manner to as
discussed in regard to FIGS. 3-5. The air supply 112 may be
implemented through various forms, such as an air pump, a
turbocharger of the engine 92, or the truck's air brake system. An
air flow sensor line 114 can be used to relay to the controller 104
the amount of air, and thus, the amount of oxygen supplied by the
air supply 112. Typically, it is assumed that all of the oxygen
supplied by the air supply 112 is consumed in combustion by the
burner 96. Thus, the amount of fuel supplied to the burner 96 can
be controlled based upon the amount of useable oxygen present in
the exhaust gas and the amount of oxygen available from the air
supply 112.
[0049] To properly control the fueling of the burner 96, the amount
of useable oxygen present in the exhaust gas from the engine 92 may
be determined. This can be done empirically in a test cell by
operating the engine 92 and the burner 96 across a range of
operating conditions. To do so, the engine 92 is operated at a
given operating condition in the test cell, and the
theoretically-calculated amount of available oxygen in the engine
exhaust gas is determined for the given operating condition. Oxygen
from the air supply 112 is also supplied to the burner 96 in a
controlled, known quantity. Fuel is supplied to the burner 96 in an
amount which should provide a desired air-to-fuel ratio (e.g.,
stoichiometric) based on the total oxygen in the exhaust gas (i.e.,
the sum of the theoretically-calculated amount of available oxygen
in the exhaust gas and the known amount supplied by the air supply
112). An oxygen sensor is used to sense the amount of oxygen
present in the exhaust gas stream downstream of the burner. Since
it is assumed that all of the oxygen supplied to the burner 96 from
the air supply 112 is consumed, the amount of oxygen sensed in the
exhaust gas stream downstream of the burner 96 represents the
amount of oxygen in the engine exhaust gas that is not consumed
(i.e., the amount of oxygen in the engine exhaust gas that is for
one reason or another "unusable" by the burner). The amount of
"useable oxygen" is the difference between the amount of oxygen
present in exhaust gas upstream of the burner 96 and the amount of
oxygen sensed in the exhaust gas downstream of the burner 96. In
other words, the amount of "useable oxygen" is the difference
between the amount of total oxygen in the exhaust gas (i.e., the
sum of the theoretically-calculated amount of available oxygen in
exhaust gas and the known amount supplied from the air supply 112)
and the amount of "unusable" oxygen in the exhaust gas (i.e., the
sensed amount of oxygen present in the exhaust gas downstream of
the burner 96).
[0050] It should be appreciated that this measurement may be
repeated across a range of operating conditions of the engine 92.
For example, the amount of useable oxygen can be determined for
various engine speeds and loads. The resulting data may be used to
create an engine map for use by the electronic controller 104.
Thus, fueling of the burner 96 may be controlled across a range of
operating conditions based upon the engine map.
[0051] FIG. 10 shows an illustrative control routine 200, which can
be used to control fueling to the burner 96 for regenerating the
particulate filter 100 based upon the amount of useable oxygen
present in the exhaust gas. The control routine 200 can be
commenced based upon various triggering events, such as comparing
the pressure across the filter 100 to a predetermined pressure
threshold or expiration of a predetermined time interval, for
example. Once the control routine 200 commences, operation 202 is
performed, which determines the amount of useable oxygen present in
the exhaust gas, such as in the manner previously described. In
operation 204, the amount of oxygen being supplied from the air
supply 112 is determined. The sensor line 114 transmits this data
to the electronic controller 104 for processing. These quantities
are used in operation 208, which adjusts the amount of fuel
supplied to the burner 96 according to closed-loop control allowing
the fueling to be continuously adjusted based upon the oxygen
amounts calculated in operations 202 and 204. The control routine
200 can end according to a particular completion event recognized
by the electronic controller 104, such as the completion of a
predetermined condition or detection of a particular operating
condition, such as the pressure drop across the substrate 42 of the
particulate filter 100 measured through a pressure sensor 124 and
transmitted through a sensor line 126.
[0052] This control strategy can also be used with other control
methods, such as that discussed in regard to FIG. 11. That is, the
determination of useable oxygen can be used to set an upper, or
maximum, limit on an amount of fuel to be supplied to the burner,
while implementing another control strategy to control the burner
96 while operating under this limit. One such maximum fueling limit
could be established at the level at which enough fuel is supplied
to the burner 96 to consume the amount of useable oxygen in the
exhaust gas and the amount provided from the air supply 112, which
could be implemented as a dynamic upper limit that depends upon
variables such as the operating conditions of the engine 92 and the
amount of oxygen supplied by the air supply 12, for example.
[0053] Another method of avoiding overfueling of the burner 96 is
to monitor the temperature of the heat generated by the burner 96,
which can be done by determining the temperature of exhaust gas
heated by the burner 96. In the illustrative embodiment of FIG. 9,
a temperature sensor 116 is shown positioned at an inlet of the
filter 100. The temperature sensor 116 generates a signal
indicating the temperature of the exhaust gas entering the filter
96 and transmits the signal through sensor line 118 for processing
by the electronic controller 104. The temperature of the heat
generated by the burner 96 typically increases as fuel being
supplied thereto is increased in quantity and as long as enough
oxygen is present for burning. However, if not enough oxygen is
present, overfueling occurs. The unburned fuel will absorb heat,
using it for vaporization. With energy being taken out of the
heated exhaust gas, the temperature of the exhaust gas flowing
along the exhaust path 94 will decrease in temperature. Thus, when
fuel being supplied to the burner 96 is being increased, but the
temperature at the inlet of the filter 100 decreases, the
electronic controller 104 can determine that overfueling has
occurred. At that point, the fuel to the burner 96 can be reduced,
which would likely result in the temperature increasing.
[0054] FIG. 11 shows an illustrative control routine 300 that can
be used to control the burner 96 to avoid the overfueling scenario.
Similar to control routine 200, the control routine 300 can
commence based upon the triggering events, such as predetermined
thresholds being reached or predetermined times occurring, such as
previously discussed herein. Once the control routine 300 has
commenced, operation 302 can occur in which the burner 96 is
activated with an air/fuel mixture being supplied thereto. In
operation 304, the flow rate of the fuel supplied to the burner 96
is increased to raise the temperature of the heat generated by the
burner in order to reach temperatures sufficient for regenerating
the filter 100.
[0055] In operation 306, the temperature of the heat generated by
the burner 96 is determined using the temperature sensor 116 and
the electronic controller 104. The determination of the heat
temperature can be performed in various manners. For example, in
one illustrative embodiment, the controller 104 can sample the
temperature at the inlet of the filter 100 over some predetermined
amount of time through the temperature sensor 116. These samples
can be stored in the memory device 108.
[0056] The processor 106 can then determine if the temperature is
decreasing over the predetermined amount of time, as is performed
in operation 308. In other words, the processor 106 can trend the
temperature over the predetermined amount of time to ensure that
the decrease in temperature is occurring for a length of time long
enough to determine that overfueling is occurring. If the
temperature trend indicates that the temperature of the heat is not
decreasing, the control routine 300 performs the operation 304 and
continues to increase the flow rate of fuel supplied to the burner
96 to increase the temperature of the burner. If the temperature is
determined to be decreasing, operation 310 is performed, which
reduces the flow rate of fuel supplied to the burner 96. After a
delay (not shown), operations 308 can again be performed to
determine if the temperature of the heat is decreasing. After
regeneration is deemed complete, or after some other condition
occurs such as the completion of a predetermined time period,
control routine 300 can end.
[0057] During operation of the engine 92, the temperature of the
SCR catalyst 102 is controlled to remove NOx from the exhaust gas.
In one illustrative embodiment, the SCR catalyst 102 is configured
to have an operating range of 200-400 degrees Celsius. The exhaust
gas flowing along the exhaust path 94 can be heated using the
burner 96 before it reaches the SCR catalyst 102, which allows it
to provide heat to the SCR catalyst 102 for operation. It is also
desirable to keep the temperature of the SCR catalyst 102 from
rising above the upper limit of its operating range to maintain its
efficiency.
[0058] During use of the SCR catalyst 102, it may become difficult
to control the temperature of the SCR catalyst 102 within its
operating range due to a number of reasons. One reason, for
example, may be that the components positioned between the burner
96 and the SCR catalyst 102, such as the DOC 98 and the filter 100,
can absorb the heat being produced by the burner 96. Thus, without
knowing how much heat the filter 100 will absorb, control of the
SCR 102 catalyst temperature can become unpredictable. Also,
typically a closed-loop control strategy is used, which, due to
delay times in component response, may cause the upper limit of the
SCR catalyst temperature range to be overshot.
[0059] One manner in which to control the temperature of the SCR
catalyst 102 without consideration of the actual SCR catalyst
temperature is to predict the amount of fuel required to heat the
SCR catalyst 102 to within its operating range based upon the flow
rate of fuel being provided to the burner. In one illustrative
embodiment, a control strategy may be implemented using the
integral of the fuel flow rate to the burner 96 (the amount of
fuel). A sensor 125 and sensor line 136 are used to sense and
transmit the fuel flow rate to the burner 96 to the electronic
controller 104, where the integral can be determined with the
microprocessor 106 providing the total amount of fuel currently
supplied to the burner 96 from some predetermined previous point in
time, such as when the burner is activated.
[0060] In another illustrative embodiment, other operating
conditions may be implemented in order to predict the amount of
fuel required to heat the SCR catalyst. For example, the normalized
exhaust flow through the burner 96 and the temperature of the
exhaust gas at the burner 96 inlet may be measured and implemented
as variables. A sensor 128 is configured to sense the flow rate of
the exhaust gas flowing through the burner. The sensor 128
transmits this data through sensor line 132 to the electronic
controller 104. A temperature sensor 130 is configured to determine
the temperature of the exhaust gas flowing through the burner 96
and transmit this data through a sensor line 134 to the electronic
controller 104.
[0061] These operating conditions can then be used either
separately or together to predict how much fuel will be needed by
the burner 96 in order to supply an amount of heat to reach the
operating range of the SCR catalyst 102 and maintain it within the
range. Furthermore, various control strategies may be implemented
using these operating conditions to predict the amount of fuel to
be supplied to the burner 96. For example, in one illustrative
embodiment, a fuzzy logic control strategy may be used. This
control strategy analyzes analog input values in terms of logical
variables that take on continuous values between 0 and 1. This
allows the input values to have various states. The states may be
defined as "membership functions" such that as an input variable
gains membership in one state, it loses membership in another.
Thus, transitioning states does not include discreet transitions
from one state to another, but rather degrees of transition. In
this example, the amount of fuel supplied to the burner may be one
of these variables. As previously discussed, the flow rate of
exhaust gas through the burner and the temperature of the exhaust
gas flowing through the burner may also be variables. This fuzzy
logic control strategy programmed into the memory device 108 of the
controller 104 and executed by the processor 106. It should be
appreciated that other control strategies may be implemented to
predict the amount of fuel to be supplied to the burner 96, such as
a Smith predictor strategy, as well as a bang-bang controller.
[0062] Referring again to FIG. 9, a temperature sensor 140
transmits the temperature of the SCR catalyst 102 through the
sensor line 142. The temperature value provided by the sensor 140
can be used along with the control strategy described above to form
an OR gate function. For example, while the prediction-based
control model is used put the temperature of the SCR catalyst 102
into operating range, if the upper limit of the range is reached
earlier than predicted, the temperature is observed by the
electronic controller 104 and the burner 96 can be deactivated.
[0063] FIG. 12 shows one illustrative control routine 400 that can
be used to adjust the SCR catalyst temperature to be within the
operating temperature range. The control routine 400 can be
commenced based upon some triggering event, a predetermined time,
or can be commenced anytime the engine is started from a "cold
start." Furthermore, the control routine 400 can be executed for
determining when to turn the burner on or off or controlling the
burner during operation as illustratively shown in FIG. 12. Once
commenced, the illustrative control routine 400 performs operation
402, which determines the amount of fuel supplied to the burner 96.
Operation 404 is then performed which determines the exhaust gas
flow rate through the burner 96. Operation 406 is then performed,
which determines the exhaust gas temperature at the inlet of the
burner 96.
[0064] Once this data is collected, operation 408 can be performed,
which determines the predicted amount of fuel to be provided to the
burner 96. As discussed, this operation may be performed using
various control strategies, such as fuzzy logic, for example.
Operation 410 includes supplying the predicted amount of fuel to
the burner 96. Operation of the burner 96 may be controlled in this
manner for a period of time until the predicted amount of fuel has
been provided to the burner. Once this operation period is
complete, the control routine 400 can end.
[0065] During operation of the burner 96, the surfaces of
electrodes 28, 30 can become fouled due to accumulation of soot or
other matter thereon. Soot/matter accumulation can contribute to
failed ignition of the burner. Once it has been determined that
burner 96 is to be shutdown until further use, the air/fuel mixture
being supplied to the burner can be adjusted to combust any soot or
other matter accumulated on the electrodes 28, 30. The fuel being
supplied to the burner 96 can be reduced, if necessary, in an
attempt to force the air/fuel mixture to a ratio greater than
stoiciometric. Providing a greater than stoiciometric, or lean,
air-to-fuel ratio will raise the temperature around the electrodes
to provide a hot enough environment to allow the various matter on
the surface of the electrodes 28, 30 to combust. During operation
of the burner, the electrodes 28, 30 are constantly being operated
in order to maintain a flame within the burner 96. Thus, the
sparking provides the ignition of the lean air/fuel mixture, which
will burn off the soot. If the fueling of the burner 96 cannot be
controlled so as to achieve a greater than stoichiometric air/fuel
mixture, the air supply 112 can be used in order to increase the
air-to-fuel ratio of the air/fuel mixture.
[0066] FIG. 13 shows an illustrative control routine 500 that can
be executed by the electronic controller 104 to combust matter
accumulated on the electrodes 28, 30. Operation 502 determines if a
shutdown request has been made. If so, the control routine 500
performs operation 504, which determines the air-to-fuel ratio of
the air/fuel mixture being supplied to the burner 96. After the
air-to-fuel ratio is determined, operation 506 is performed which
adjusts the air-to-fuel ratio of the air/fuel mixture being
supplied to the burner if adjustment is required. If the
air-to-fuel ratio requires adjustment to a
greater-than-stoichiometric ratio, the adjustment can be performed
by reducing the amount of fuel being supplied to the burner 96
and/or through supplying oxygen from the air supply 112.
[0067] After adjustment, or if none is necessary, operation 508 is
performed, which operates the burner 96 for a predetermined amount
of time allowing the soot, or other matter, to be burned off the
surfaces of the sparking electrodes 28, 30. It should be
appreciated that increasing the air-to-fuel ratio may physically
move the flame in the combustion chamber such that it moves towards
the electrodes 28, 30, which can burn of soot or other matter
accumulated on the electrode surfaces. After the predetermined
amount of time has elapsed, operation 510 is performed to shutdown
the burner 96, which can be done using the electronic controller
104.
[0068] 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.
[0069] 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.
[0070] 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.
* * * * *