U.S. patent application number 11/494525 was filed with the patent office on 2008-01-31 for power source thermal management and emissions reduction system.
This patent application is currently assigned to Caterpillar Inc.. Invention is credited to Scott Alan Leman, David Andrew Pierpont.
Application Number | 20080022657 11/494525 |
Document ID | / |
Family ID | 38981035 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080022657 |
Kind Code |
A1 |
Pierpont; David Andrew ; et
al. |
January 31, 2008 |
Power source thermal management and emissions reduction system
Abstract
A power source may have at least one combustion chamber, a first
valve configured to control an airflow between an air source and
the at least one combustion chamber and a second valve configured
to control an exhaust gas flow between the combustion chamber and
an exhaust system. The power source may also have a fuel source
configured to supply a fuel to the at least one combustion chamber
and a controller operatively connected to the first valve and the
second valve. The controller may be configured to determine one or
more temperatures and, if the one or more temperatures are below a
predetermined threshold, cause the first valve to substantially
limit the airflow to the combustion chamber and cause the second
valve to substantially limit the exhaust gas flow from the
combustion chamber, such that a combustion stroke of one or more
combustion cycles is executed with air substantially provided
during an intake stroke of a previous combustion cycle.
Inventors: |
Pierpont; David Andrew;
(Dunlap, IL) ; Leman; Scott Alan; (Eureka,
IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Caterpillar Inc.
|
Family ID: |
38981035 |
Appl. No.: |
11/494525 |
Filed: |
July 28, 2006 |
Current U.S.
Class: |
60/285 ;
123/90.15; 60/295; 60/297 |
Current CPC
Class: |
F02D 41/1446 20130101;
F02D 13/06 20130101; F02D 41/024 20130101; Y02T 10/12 20130101;
F02B 1/12 20130101; F02D 41/3058 20130101; F02B 37/00 20130101;
Y02T 10/18 20130101 |
Class at
Publication: |
60/285 ; 60/295;
60/297; 123/90.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34; F01N 3/00 20060101 F01N003/00 |
Claims
1. A power source, comprising: at least one combustion chamber; a
first valve configured to control an airflow between an air source
and the at least one combustion chamber; a second valve configured
to control an exhaust gas flow between the combustion chamber and
an exhaust system; a fuel source configured to supply a fuel to the
at least one combustion chamber; and a controller operatively
connected to the first valve and the second valve, wherein the
controller is configured to: determine one or more temperatures;
and if the one or more temperatures are below a predetermined
threshold, cause the first valve to substantially limit the airflow
to the combustion chamber and cause the second valve to
substantially limit the exhaust gas flow from the combustion
chamber, such that a combustion stroke of one or more combustion
cycles is executed with air substantially provided during an intake
stroke of a previous combustion cycle.
2. The power source of claim 1, further including a particulate
filter fluidly connected to the exhaust gas system.
3. The power source of claim 2, wherein the one or more
temperatures include at least one of an exhaust gas temperature, a
particulate filter temperature, or a temperature associated with
the power source.
4. The power source of claim 2, wherein the particulate filter is
configured for passive regeneration.
5. The power source of claim 1, wherein the predetermined threshold
is between about 200 degrees C. and about 350 degrees C.
6. The power source of claim 1, further including: a selective
catalytic reduction system fluidly connected to the exhaust
system.
7. A power source, comprising: at least one combustion chamber; an
intake passage fluidly connected to the at least one combustion
chamber; an intake valve disposed between the intake passage and
the combustion chamber; an airflow control element, independent of
the intake valve and configured to, upon activation, substantially
limit an airflow from entering the combustion chamber; an exhaust
passage fluidly connected to the at least one combustion chamber;
an exhaust valve disposed between the exhaust gas passage and the
combustion chamber; an exhaust flow control element independent of
the exhaust valve and configured to, upon activation, substantially
limit an exhaust gas from exiting the combustion chamber; a fuel
source configured to supply a fuel to the at least one combustion
chamber; and a controller operatively connected to the airflow
control element and the exhaust flow control element, wherein the
controller is configured to: determine one or more temperatures;
and if the one or more temperatures are below a predetermined
threshold, activate both the exhaust flow control element and the
airflow control element, such that airflow is substantially limited
from entering the combustion chamber and exhaust gas is
substantially limited from leaving the combustion chamber for at
least one subsequent combustion stroke.
8. The power source of claim 7, further including a particulate
filter fluidly connected to the exhaust gas passage.
9. The power source of claim 7, wherein the one or more
temperatures include at least one of an exhaust gas temperature, a
particulate filter temperature, or a temperature associated with a
power source .
10. The power source of claim 7, wherein the particulate filter is
configured for passive regeneration.
11. The power source of claim 10, wherein the predetermined
threshold is between about 200 degrees C. and about 350 degrees
C.
12. The power source of claim 7, further including: a selective
catalytic reduction system fluidly connected to the exhaust
passage.
13. A method for operating a power source, the method comprising:
providing at least a first fuel charge and a first air charge to a
combustion chamber of a power source; combusting the first fuel
charge in the combustion chamber resulting in an exhaust gas;
determining one or more temperatures; and if the one or more
temperatures are below a predetermined threshold: activating an
airflow control element configured to substantially limit a second
air charge from entering the combustion chamber; activating an
exhaust flow control element configured to substantially limit the
exhaust gas from exiting the combustion chamber; and combusting at
least one subsequent fuel charge within the combustion chamber
prior to deactivating the airflow control element and the exhaust
flow control element.
14. The method of claim 13, wherein the one or more temperatures
include at least one of an exhaust gas temperature, a particulate
filter temperature, or a temperature associated with the power
source.
15. The method of claim 13, wherein the at least one subsequent
fuel charge is combusted such that the one or more temperatures are
maintained above about 200 degrees C.
16. The method of claim 13, further including: de-activating the
exhaust flow control element following the combustion of the at
least one subsequent fuel charge; causing the exhaust gas to be
exposed to a regenerative particulate filter.
17. The method of claim 16, wherein the regenerative particulate
filter is configured for passive regeneration.
18. The method of claim 17, further including: providing a
particulate filter regenerative catalyst material to the exhaust
gas.
19. The method of claim 13, further including: providing a
reductant substance to the exhaust gas; exposing the exhaust gas
and the reductant to a selective catalytic reduction catalyst.
20. The method of claim 13, further including: determining a
remaining air charge within the combustion chamber; if the
remaining air charge is below a predetermined limit, deactivating
the airflow control element such that fresh air may be provided to
the combustion chamber.
21. The method of claim 20, wherein the determination is based on
at least one of power source load, combustion chamber volume, power
source rotational speed, or experimental data.
22. A machine, comprising: a frame; a traction device; and a power
source operatively connected to the frame and the traction device,
wherein the power source includes: at least one combustion chamber;
a first valve configured to control an airflow between an air
source and the at least one combustion chamber; a second valve
configured to control an exhaust gas flow between the combustion
chamber and an exhaust system; a fuel source configured to supply a
fuel to the at least one combustion chamber; and a controller
operatively connected to the first valve and the second valve,
wherein the controller is configured to: determine one or more
temperatures; and if the one or more temperatures are below a
predetermined threshold, cause the first valve to substantially
limit the airflow to the combustion chamber, and cause the second
valve to substantially limit the exhaust gas flow from the
combustion chamber such that a combustion stroke of one or more
combustion cycles is executed with air substantially provided
during an intake stroke of a previous combustion cycle.
Description
TECHNICAL FIELD
[0001] This disclosure pertains generally to reduction of
particulate and other emissions from a power source and, more
particularly, to the use of variable valve operation for thermal
management and emission control.
BACKGROUND
[0002] Government standards associated with combustion engine
emissions have increased the burden on manufacturers to reduce the
amount of particulate and other emissions that may be exhausted
from their engines. For example, Environmental Protection Agency
regulations require a 90 percent reduction in emissions of oxides
of nitrogen (NOx) and particulate matter (e.g., hydrocarbons and
soot) for the year 2007. Manufacturers also have a commitment to
their customers to produce powerful yet fuel efficient engines.
However, the sometimes inverse relationship between fuel
economy/power and reduced emissions tends to make the task of
reducing emissions while meeting customer needs a daunting one.
[0003] Exhaust after-treatment systems, including regenerative
particulate filters (RPFs) and selective catalytic reduction (SCR),
provide methods for removing particulate and other emissions (e.g.,
NOx) from fossil fuel powered systems for engines, factories, and
power plants. RPFs may capture particulate matter within exhaust
gas, composed primarily of unburned hydrocarbons, and then oxidize
the particulate matter, using active or passive regeneration
cycles, into carbon dioxide and water, among other things. During
typical SCR, a catalyst may facilitate a reaction between exhaust
gas NOx and a reductant, for example, ethanol, to produce nitrogen
gas and byproduct substances such as water and nitrogen, thereby
removing NOx from the exhaust gas. It is important to note that
while the term "exhaust gas" may indicate a substance that is
primarily gas phase, exhaust gas, as a byproduct of combustion, may
also contain substances in solid or liquid phase. For example,
particulate matter described herein may be included within exhaust
gas and may be in solid or liquid phase. One of skill in the art
will understand that the term "exhaust gas" is intended to refer to
all such substances generated as a byproduct of combustion.
[0004] By capturing particulate matter, particulate filters may
eventually become clogged and unusable without a method for
"regeneration." Regeneration may be passive or active and is the
process by which a particulate filter may "remove" the collected
particulate matter by oxidation (e.g., burning). A negligible
amount of ash may remain in the particulate filter following
regeneration, and such accumulations may be cleaned manually at
desired intervals.
[0005] Active regeneration may involve the addition of heat, such
as electrical resistance heat, to an RPF to facilitate oxidation of
the particulate matter. Passive regeneration may facilitate
oxidation of the particulate matter in the presence of a catalyst,
without the addition of heat, provided the exhaust gas is
maintained at a minimum oxidation temperature (e.g., above about
200 degrees C.). When the exhaust gas temperature falls below the
minimum oxidation temperature, the passive RPF may be unable to
successfully oxidize particulate matter and the flow of exhaust
through the RPF may, therefore, be reduced or stopped due to the
trapped particulate matter. Limited exhaust flow may, in turn,
cause increased backpressure in the exhaust system. Such increased
backpressure may then lead to significant performance degradation
and a possible uncontrolled regeneration event within the RPF.
Uncontrolled regeneration may further lead to a cracked or
otherwise damaged RPF among other things. For example, under cold
start and/or low load conditions (e.g., engine idle or near idle),
exhaust gas temperatures may fall below the minimum oxidation
temperature. The passively regenerated particulate filter may then
begin to fill with particulate matter and the exhaust backpressure
may increase. Oxidation of the trapped particulate matter may then
occur in an uncontrolled burn resulting in damage or destruction of
the RPF. Because of this, many engines utilizing passively
regenerated particulate filters must be supplemented by an active
regeneration or other similar system to facilitate controlled
regeneration at exhaust temperatures below the minimum oxidation
temperature.
[0006] An SCR system typically includes injection and mixing of a
reductant (e.g., ethanol) into the exhaust gas upstream of a
catalyst to facilitate a reaction in the presence of the catalyst.
Operation of an SCR after-treatment system may also depend upon
maintaining a minimum temperature of both the catalyst and the
exhaust gas, with higher temperatures generally improving the
reaction between the reductant and NOx. While the performance of a
lean-NOx catalyst to reduce NOx may depend upon many factors, such
as catalyst formulation, the size of the catalyst, mixing of the
reductant within the gas, the reductant compound, and reductant
dosing rate, it is important that the minimum temperature be
maintained such that the SCR continues to operate effectively.
Therefore, under cold start and low load conditions (e.g., engine
idle or near idle), where the exhaust-gas temperature falls below a
minimum reaction temperature, the efficiency of the SCR
after-treatment may be greatly reduced or the reaction halted
resulting in increased NOx emissions.
[0007] Lean burn power sources may operate with an excess amount of
air for each power cycle and depending on operating conditions
(e.g., load, temperature, etc.), the excess may be three to ten
times the amount of air necessary to combust fuel present in the
combustion chamber. This may result in more complete combustion of
the fuel and greater fuel efficiency. Once the fuel in the
combustion chamber is burned, the excess air (now heated from
combustion), as well as any remaining hydrocarbons may be exhausted
with the exhaust gas generated by combustion to the exhaust system.
While the lean mixture may result in greater fuel efficiency, such
a mixture may also lead to higher combustion temperatures and
therefore greater NOx production. Some power sources may rely on
methods such as exhaust gas recirculation, for example, to lower
combustion chamber temperatures and reduce NOx formation. But lower
combustion chamber temperatures, particularly at low load, may lead
to lower exhaust-gas temperatures, which may in turn decrease or
terminate the operation of exhaust after-treatment systems.
[0008] Some power sources may rely on combustion chamber
deactivation to warm exhaust after-treatment systems at cold start,
increase fuel economy, and reduce power source emissions output at
low loads. The term "combustion chamber" may be used
interchangeably with the term "cylinder" throughout this
disclosure. It is to be understood that an engine cylinder may
include a combustion chamber and, therefore, "cylinder" may also
refer to a combustion chamber. Such power sources may include
mechanisms for disabling a group of cylinders within the power
source by stopping the flow of fuel to the targeted cylinders. For
example, a six cylinder power source may include a variable valve
mechanism to stop intake valve operation and fuel delivery for
three of the six cylinders, effectively shutting off those three
cylinders. While such a system may be useful for increasing fuel
efficiency and reducing emissions output from the power source, the
systems may be unable to maintain a minimum exhaust temperature to
facilitate operation of an exhaust after-treatment system at low
loads or idle while also responding quickly to increased demand for
power.
[0009] One system using cylinder deactivation for limiting cold
start emissions is disclosed in U.S. Patent No. 6,931,839 to Foster
("the '839 patent"). The system of the '839 patent includes a
mechanism for redirecting fuel flow, disabling spark, and
preventing movement of intake and exhaust valves such that a group
of cylinders may be deactivated during a cold engine start. A
portion of the fuel that would normally be burned in the
deactivated group of cylinders is re-directed to the remaining
active cylinders thereby leading to an increase in torque to
overcome the added resistance of the deactivated cylinders.
Further, combustion temperature in the active cylinders is
increased via the increase in fuel combusted, which in turn leads
to higher exhaust gas temperatures and faster warming of the
catalytic converter to operating temperature.
[0010] While the system of the '829 patent may result in some
additional heat added to the exhaust gas, it requires that a group
of cylinders be deactivated via disruption of fuel flow, thereby
operating the power source in a less than optimal state. Operation
under such conditions may lead to balance issues and may render a
power source less responsive to power demands, as the inactive
cylinders must be reactivated upon heavy load demand. Further,
deactivating a group of cylinders, while injecting additional fuel
into the remaining active cylinders may lead to a rich mixture
thereby reducing fuel economy and potentially increasing
hydrocarbon emissions. Moreover, the additional temperature
increase derived from the combustion of additional fuel in active
cylinders may not warm the exhaust gas and exhaust after-treatment
systems as quickly as if all cylinders were operating at an
increased combustion temperature.
[0011] The present disclosure is directed at overcoming one or more
of the problems or disadvantages in the prior art power
systems.
SUMMARY OF THE DISCLOSURE
[0012] In one aspect, the present disclosure is directed to a power
source. The power source may include at least one combustion
chamber, a first valve configured to control an airflow between an
air source and the at least one combustion chamber, and a second
valve configured to control an exhaust gas flow between the
combustion chamber and an exhaust system. The power source may also
include a fuel source configured to supply a fuel to the at least
one combustion chamber and a controller operatively connected to
the first valve and the second valve. The controller may be
configured to determine one or more temperatures and, if the one or
more temperatures are below a predetermined threshold, cause the
first valve to substantially limit the airflow to the combustion
chamber and cause the second valve to substantially limit the
exhaust gas flow from the combustion chamber, such that a
combustion stroke of one or more combustion cycles is executed with
air substantially provided during an intake stroke of a previous
combustion cycle.
[0013] In another aspect, the present disclosure is directed to a
power source. The power source may include at least one combustion
chamber, an intake passage fluidly connected to the at least one
combustion chamber, an intake valve disposed between the intake
passage and the combustion chamber, and an airflow control element,
independent of the intake valve and configured to, upon activation,
substantially limit an airflow from entering the combustion
chamber. The power source may also include an exhaust passage
fluidly connected to the at least one combustion chamber, an
exhaust valve disposed between the exhaust gas passage and the
combustion chamber, an exhaust flow control element independent of
the exhaust valve and configured to, upon activation, substantially
limit an exhaust gas from exiting the combustion chamber, a fuel
source configured to supply a fuel to the at least one combustion
chamber, and a controller operatively connected to the airflow
control element and the exhaust flow control element. The
controller may be configured to determine one or more temperatures
and, if the one or more temperatures are below a predetermined
threshold, activate both the exhaust flow control element and the
airflow control element, such that airflow is substantially limited
from entering the combustion chamber and exhaust gas is
substantially limited from leaving the combustion chamber for at
least one subsequent combustion stroke.
[0014] In yet another aspect, the present disclosure is directed to
a method for operating a power source. The method may include the
steps of providing at least a first fuel charge and a first air
charge to a combustion chamber of a power source, combusting the
first fuel charge in the combustion chamber resulting in an exhaust
gas, and determining one or more temperatures. If the one or more
temperatures are below a predetermined threshold, the method may
further include the steps of activating an airflow control element
configured to substantially limit a second air charge from entering
the combustion chamber, activating an exhaust flow control element
configured to substantially limit the exhaust gas from exiting the
combustion chamber, and combusting at least one subsequent fuel
charge within the combustion chamber prior to deactivating the
airflow control element and the exhaust flow control element.
[0015] In yet another aspect, the present disclosure is directed to
a machine. The machine may include a frame, a traction device, and
a power source operatively connected to the frame and the traction
device. The power source may include at least one combustion
chamber, a first valve configured to control an airflow between an
air source and the at least one combustion chamber, a second valve
configured to control an exhaust gas flow between the combustion
chamber and an exhaust system, a fuel source configured to supply a
fuel to the at least one combustion chamber, and a controller
operatively connected to the first valve and the second valve. The
controller may be configured to determine one or more temperatures
and, if the one or more temperatures are below a predetermined
threshold, cause the first valve to substantially limit the airflow
to the combustion chamber, and cause the second valve to
substantially limit the exhaust gas flow from the combustion
chamber such that a combustion stroke of one or more combustion
cycles is executed with air substantially provided during an intake
stroke of a previous combustion cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 provides a pictorial representation of an exemplary
machine having multiple systems and components that may cooperate
to accomplish a task;
[0017] FIG. 2 schematically illustrates a power source capable of
implementing the disclosed systems and methods for thermal
management and emissions reduction; and
[0018] FIG. 3 is a flowchart depicting one exemplary method for
operation of the disclosed systems and methods.
DETAILED DESCRIPTION
[0019] FIG. 1 provides a pictorial representation of an exemplary
machine 5 having multiple systems and components that may cooperate
to accomplish a task. Machine 5 may include a system for thermal
management and emissions reduction. Machine 5 may embody a fixed or
mobile machine that performs some type of operation associated with
an industry such as mining, construction, farming, transportation,
or any other industry known in the art. For example, machine 5 may
be an earth moving machine such as an excavator, a dozer, a loader,
a backhoe, a motor grader, a dump truck, or any other earth moving
machine. In addition, machine 5 may be an on- or off-road vehicle
including, for example, heavy and light trucks or an automobile.
Machine 5 may include a power source 18 and an input member 16
connecting a transmission assembly 10 to power source 18 via a
torque converter 19. Machine 5 may also include a frame 14 and an
output member 20 connecting the transmission assembly 10 to one or
more traction devices 77 operatively connected to frame 14. Power
source 18 may be operatively connected to frame 14 and may further
be fluidly connected to an exhaust system 17, which may in turn be
fluidly connected to an RPF 23 and/or an SCR system catalyst
31.
[0020] FIG. 2 schematically illustrates a power source capable of
implementing the disclosed systems and methods for thermal
management and emissions reduction. In an exemplary emissions
reduction system, power source 18 includes an internal combustion
engine, e.g., a diesel engine, a gasoline engine, a gaseous
fuel-powered engine, and the like, or any other lean-burn engine
apparent to one skilled in the art. Power source 18 may include,
for example, an intake manifold 26, intake passages 24; exhaust
passages 29, an exhaust manifold 28, combustion chambers 30,
airflow control elements 25, exhaust flow control elements 27, and
fuel sources 38. Power source 18 may further include a fuel pump
34, fuel storage 36, and a controller 52.
[0021] Each of combustion chambers 30 may be configured with a
slideably mounted piston (not shown) and may be configured to
receive and combust materials including fuel and air, among other
things (e.g., performance enhancing substances). A piston
associated with a combustion chamber from combustion chambers 30
may be connected to a crankshaft (not shown) such that a rotation
of the crankshaft results in a corresponding reciprocating motion
of the piston.
[0022] Power source 18 may be configured to operate using a
two-stroke, four-stroke, or any other suitable combustion cycle. A
"stroke" may be defined as one-half rotation of the crankshaft
wherein the piston moves from top-dead-center to bottom-dead center
or vice versa. A standard combustion cycle may be based on power
source configuration and defined as one complete set of piston
strokes resulting in combustion of a fuel within combustion
chambers 30 and a derivation of heat/power from the combustion. For
example, a four-stroke combustion cycle may include an intake
stroke during which, air is provided to the combustion chamber, a
compression stroke during which, the air is compressed, a
combustion stroke during which, fuel is combusted and power derived
as the piston is driven downward by the resulting expansion of
gases, and an exhaust stroke during which, the resulting gases are
expelled from the combustion chamber. Other suitable combustion
cycles known in the art may also be used without departing from the
scope of this disclosure.
[0023] Combustion chambers 30 may be configured for compression
ignition (CI), spark ignition (SI), homogeneous charge compression
ignition (HCCI), or any other type of combustion ignition. For
example, a diesel engine may initiate combustion as pistons (not
shown) within combustion chambers 30 near top-dead-center and
critical temperature and pressure are reached.
[0024] Combustion chambers 30 may be configured to receive a supply
of fuel from fuel sources 38. Fuel sources 38 may include injectors
or atomizers configured to inject fuel directly into combustion
chambers 30. Fuel sources 38 may be configured to supply fuel at a
specific time (timed injection) or, alternatively, may be
configured to introduce fuel continuously or at random intervals.
Configuration of fuel sources 38 may depend upon the combustion
configuration of combustion chambers 30 (e.g., CI, SI, or HCCI and
two-stroke, four-stroke, or other suitable configuration).
[0025] Fuel sources 38 may be operatively connected to fuel pump
34. Fuel pump 34 may be configured to deliver fuel from fuel
storage 36 to fuel sources 38. Fuel pump 34 may include an
injection pump of the rotary or distributor variety, or any other
suitable pump, and may be driven indirectly by gears or chains from
the crankshaft or by other methods (e.g., electrically). One of
skill in the art will recognize that many types of pumps may
function adequately and fall within the scope of the current
disclosure.
[0026] The fuel supplied to combustion chambers 30 may include, for
example, diesel fuel, gasoline, alcohols, propane, methane, or any
other suitable fuel. The fuel may be supplied to fuel sources 38
under pressure, and/or fuel sources 38 may, themselves, be
configured to further increase the pressure or velocity of the
fuel. Fuel storage 36 may be configured to store fuel, among other
things, and may include a tank or other similar container. Fuel may
be supplied at timed intervals (e.g., based on power source 18
rotational position), randomly, and/or continuously. Control of the
fuel source 38 may be regulated by methods known by those of
ordinary skill in the art and appropriate for the type of power
source in operation.
[0027] Intake manifold 26 may be configured to draw air from
atmosphere or from an air source (e.g., a turbocharger) and provide
an air charge to combustion chambers 30 via intake passages 24. For
example, intake manifold 26 may be fluidly connected to a forced
induction system such as the outlet of a turbocharger or
supercharger. Intake manifold 26 may further be fluidly connected
to at least one intake passage 24 which, in turn, may be fluidly
connected to a combustion chamber 30. Fuel or other additive
substances (e.g., performance boosting substances including
propane) may also be supplied to intake manifold 26.
[0028] Intake passages 24 may be configured to carry substances
including, air, fuel, and other substances, or any combination
thereof, to combustion chambers 30. For example, at power source
idle operation, intake passages 24 may be configured to provide an
air charge to combustion chambers 30 containing between about three
and ten times the amount of air necessary to execute one combustion
stroke of a combustion cycle.
[0029] Intake passages 24 may be opened to combustion chambers 30
via intake valve assemblies (not shown) and/or airflow control
elements 25 which may open and close as desired to facilitate,
substantially limit, or stop the flow of materials (e.g., air) into
combustion chambers 30. Airflow control elements 25 may include
valves, flaps, actuators, and other components suitable for
enabling or limiting flow of a gas through a passage (e.g., intake
passages 24). Airflow controls elements 25 may function as and take
the place of intake valve assemblies, or alternatively, both
airflow control elements 25 and intake valve assemblies (not shown)
may be present. Further, airflow control elements 25 may operate
independently of separate intake valve assemblies (where present)
or may operate in tandem to control airflow to combustion chambers
30. Additionally, it is important to note that airflow control
elements 25 may be located in any location suitable for
substantially limiting or stopping the flow of air to combustion
chambers 30. For example, airflow control elements 25 may be
located within intake manifold 26 or at an air source.
[0030] Airflow control elements 25 and intake valve assemblies
associated with combustion chambers 30 may be directly or
indirectly connected to the crankshaft by way of a timing device
such that a rotation of the crankshaft results in corresponding
opening and closing movements of the associated control or
assembly. In addition, airflow control elements 25 and intake valve
assemblies may include mechanical and/or electro-mechanical systems
and may be activated or operated using any suitable method (e.g.,
pushrod, solenoid, etc.) to allow, substantially limit, or stop the
flow of air to combustion chambers 30. Further, airflow control
elements 25 and intake valve assemblies maybe operatively connected
to controller 52 such that controller 52 may affect an activation
or deactivation of both airflow control elements 25 and intake
valve assemblies. Intake passages 24 may contain more or fewer
elements as desired.
[0031] Combustion of a first fuel charge within combustion chambers
30 may result in at least a portion of the fuel reacting with a
portion of an air charge provided to combustion chambers 30 during
an intake stroke. Heat and/or power may be derived from the
combustion of the fuel and air and, as a result, an exhaust gas
including particulate matter (e.g., unburned hydrocarbons), NOx,
CO.sub.2, and water, among other things, may be generated. Because
the initial air charge may have contained three to ten times the
amount of air necessary for combustion, the exhaust gas may be
mixed with remaining air within combustion chambers 30. Depending
on current temperatures and operating conditions, the remaining air
within combustion chambers 30 may allow subsequent combustion
strokes to be executed within combustion chambers 30 without the
introduction of additional air and without allowing the generated
exhaust gas to exit combustion chambers 30.
[0032] Exhaust passages 29 may be fluidly connected to combustion
chambers 30 and configured to receive the exhaust gas generated as
a result of combustion of the fuel within combustion chambers 30.
The fluid connection from combustion chambers 30 to exhaust
passages 29 may be opened and closed via exhaust valve assemblies
(not shown) and/or exhaust flow control elements 27 which may open
and close as desired to facilitate, substantially limit, or stop
the flow of materials (e.g., exhaust) out of combustion chambers
30. Exhaust flow control elements 27 may include valves, flaps,
actuators, and other components suitable for enabling or limiting
flow of a gas through a passage (e.g., exhaust passages 29).
Exhaust flow control elements 27 may function as and take the place
of exhaust valve assemblies, or alternatively, both exhaust flow
control elements 27 and exhaust valve assemblies (not shown) may be
present. Further, exhaust flow control elements 27 may operate
independently of exhaust valve assemblies (where present) or may
operate in tandem to control exhaust flow from combustion chambers
30. Additionally, it is important to note that exhaust flow control
elements 27 may be located in any location suitable for
substantially limiting or stopping the flow of exhaust from
combustion chambers 30. For example, exhaust flow control elements
27 may be located within exhaust manifold 28 or within exhaust
system 17.
[0033] Exhaust flow control elements 27 and exhaust valve
assemblies associated with combustion chambers 30 may be directly
or indirectly connected to the crankshaft by way of a timing device
such that a rotation of the crankshaft results in corresponding
opening and closing movements of the associated control or
assembly. In addition, exhaust flow control elements 27 and exhaust
valve assemblies may include mechanical and/or electromechanical
systems and may be activated or operated using any suitable method
(e.g., pushrod, solenoid, etc.) to allow, substantially limit, or
stop the flow of an exhaust gas from combustion chambers 30.
Further, exhaust flow control elements 27 and exhaust valve
assemblies may be operatively connected to controller 52 such that
controller 52 may affect an activation or deactivation of both
exhaust flow control elements 25 and exhaust valve assemblies.
[0034] Exhaust passages 29 may also be fluidly connected to an
additive supply device 44 configured to provide an SCR reductant
and/or an RPF catalyst to the exhaust gas. For example, additive
supply device may inject an SCR reductant (e.g., ethanol or urea),
to exhaust gas flowing out of combustion chambers 30 such that upon
reaching SCR system catalyst 31, NOx emissions may be reduced.
Although additive supply device 44 is depicted in FIG. 2 as being
fluidly connected to exhaust system 17, additive supply device 44
may be located at any suitable location for providing an additive
to the exhaust gas. For example, additive supply device 44 may also
be located at exhaust manifold 28, exhaust passages 29, exhaust
system 17, or any other suitable location for providing an additive
to the exhaust gas stream.
[0035] Exhaust manifold 28 may be fluidly linked to at least one
exhaust passage 29 and may collect and receive an exhaust gas from
the at least one exhaust passage 29. Exhaust manifold may operate
to link several exhaust passages 29 together and receive the
cumulative exhaust from exhaust passages 29. Exhaust manifold 28
may further include devices for supplying other substances (e.g.,
urea, ethanol, etc.) for mixture in the exhaust gas, or,
alternatively, no such additional devices may be present. For
example, exhaust manifold 28 may be fluidly connected to additive
supply device 44, which may be configured to supply an SCR
reductant and/or an RPF catalyst additive to exhaust manifold 28.
Exhaust manifold 28 may be well insulated to prevent heat loss and
assist in maintaining exhaust temperatures conducive for operation
of an RPF and/or an SCR system.
[0036] Exhaust manifold 28 may include sensors (not shown) for
detecting exhaust-gas temperatures, levels of exhaust-gas
pollutants, and levels of other substances within the exhaust gas.
Where the sensors indicate low exhaust-gas temperatures, controller
52 may cause appropriate steps to be taken to increase exhaust-gas
temperatures (e.g., activating airflow control elements 25 and
exhaust flow control elements 27, among other things). Exhaust
manifold 28 may further include fluid connections to allow for
recirculation of some exhaust gas and/or coupling of exhaust gas to
the turbine of a turbocharger (not shown), among other things.
[0037] Exhaust manifold 28 may be fluidly connected to an exhaust
system 17, which may be configured to receive the exhaust gas from
exhaust manifold 28. Exhaust system 17 may include pipes, tubes,
clamps, etc., and may direct the flow of the exhaust gas in various
directions. Exhaust system 17 may also include sensors, mixing
devices, and fluid connections to recirculation devices and
turbocharger turbines (not shown), among other things.
[0038] RPF 23 may be fluidly connected to exhaust system 17
downstream of exhaust manifold 28 and configured to receive an
exhaust gas. RPF 23 may be constructed from many materials and may
be configured to remove particulate matter from the exhaust gas
using physical, chemical, or other suitable methods, and any
combination thereof. For example, a particulate filter utilizing
physical methods of filtration may be manufactured from
semi-penetrable or semi-porous materials including coredierite
and/or silicon carbide. The filter may include a honeycomb type
structure and each channel within the structure may be blocked at
alternating ends. Such a configuration may force exhaust gas
flowing into RPF 23 to pass through the semi-penetrable material
into a surrounding channel. While exhaust gas may pass through the
semi-penetrable material, particulate matter within the exhaust gas
may be trapped on the walls of the semi-penetrable material,
thereby removing the matter from the exhaust gas. Other types of
filters and materials may also be used including, for example,
sintered metal plates, foamed metal structures, fiber mats, and any
other suitable filtration mediums.
[0039] RPF 23 may include a passively or actively regenerated
particulate filter, or may be a combination thereof. Regeneration
of a particulate filter may be useful for substantially limiting or
eliminating accumulation of particulate matter within RPF 23. For
example, a passively regenerated particulate filter may combust
particulate matter within RPF 23 in the presence of a catalyst
material and while exhaust temperatures are maintained above a
predetermined temperature. Therefore, RPF 23 may include a metal
promoter or catalyst dispersed within the filter material. The
catalyst material may be designed to facilitate combustion or
oxidation of particulate matter within RPF 23 such that substantial
accumulation of particulates does not occur within RPF 23. Such
catalyst materials may include coatings of precious metals (e.g.,
platinum, silver, etc.) on the filter substrate. Additionally,
injection of catalytic materials (e.g., heavy metals) into the
exhaust gas stream, combustion chamber, or other suitable locations
may also be used to aid in regeneration of RPF 23.
[0040] Passive RPF regeneration may oxidize particulate matter
(e.g., carbon and hydrocarbon materials) and may proceed via
multiple complex chemical reactions. Simplified reactions may be
summarized by the following equations:
C+O.sub.2.fwdarw.CO.sub.2 (1)
NO.sub.2+C.fwdarw.NO.fwdarw.+CO.sub.2 (2)
NO+O.sub.2.fwdarw.NOx (3)
[0041] Carbon present in particulate matter may be combusted in the
presence of oxygen to produce CO.sub.2 as shown in equation 1. By
reacting in the presence of a catalyst, the oxidation reaction may
be initiated at temperature between about 200 degrees C. and 350
degrees C. As shown in equation 2, it may further be possible to
react particulate matter with NO.sub.2 to form NO and CO.sub.2. The
resulting NO may then react with available O.sub.2 to re-form
NO.sub.2 as illustrated by equation 3. While NO.sub.2 is a NOx
variant, the resultant NO.sub.2 may subsequently be treated
utilizing SCR system catalyst 31 and a SCR reductant (e.g.,
ethanol) introduced to the exhaust gas stream, or by other suitable
methods.
[0042] SCR system catalyst 31 may be disposed in exhaust system 17
downstream of RPF 23, or, alternatively, may be disposed upstream
of RPF 23 as desired. Exhaust system 17 may direct flow of the
exhaust gas such that the exhaust gas is received by SCR system
catalyst 31 and caused to contact the contained catalytic
materials.
[0043] SCR system catalyst 31 may be made from a variety of
materials. SCR system catalyst 31 may include a catalyst support
material and a metal promoter dispersed within the catalyst support
material. The catalyst support material may include at least one of
alumina, zeolite, aluminophosphates, hexaluminates,
aluminosilicates, zirconates, titanosilicates, and titanates. In
one embodiment, the catalyst support material may include at least
one of-alumina and zeolite, and the metal promoter may include
silver metal (Ag). Combinations of these materials may be used, and
the catalyst material may be chosen based on the type of fuel used,
the ethanol additive used, the air to fuel-vapor ratio desired,
and/or for conformity with environmental standards. One of ordinary
skill in the art will recognize that numerous other catalyst
compositions may be used without departing from the scope of this
disclosure. Further, multiple SCR system catalysts may also be
included in exhaust system 17.
[0044] The lean-NOx catalytic reaction is a complex process
including many steps. One of the reaction mechanisms, however, that
may proceed in the presence of SCR system catalyst 31 can be
summarized by the following reaction equations:
HC+O.sub.2 oxygenated HC (4)
NOx+oxygenated HC+O.sub.2.fwdarw.N.sub.2+CO.sub.2+H.sub.2O (5)
[0045] SCR system catalyst 31 may catalyze the reduction of NOx to
N.sub.2 gas, as shown in equation (5). Further, as shown in
equation (4), a hydrocarbon reducing agent may be converted to an
activated, oxygenated hydrocarbon that may interact with the NOx
compounds to form organo-nitrogen containing compounds. These
materials may possibly decompose to isocyanate (NCO) or cyanide
groups and eventually yield nitrogen gas (N.sub.2) through the
series of reactions as summarized above. A well mixed reductant
(e.g., ethanol) within the exhaust gas may further react in the
presence of any remaining hydrocarbons (e.g., unburned fuel) in
order to aid in the production of oxygenated hydrocarbons, as
represented by equation (4).
[0046] Controller 52 may be a mechanical or an electrical based
controller configured to control fuel flow, airflow, and exhaust
flow, among other things, to and from combustion chambers 30.
Controller may also be operatively connected to intake and exhaust
valves and/or airflow control elements 25 and exhaust flow control
elements 27. For example, controller 52 may send electric signals
causing intake and exhaust valves and/or airflow control elements
25 and exhaust flow control elements 27 to open and close thereby
allowing, substantially limiting, or stopping the flow of air and
exhaust to and from combustion chambers 30. Flow control may be
based on factors including RPF temperature, SCR system catalyst
temperature, exhaust-gas temperature, power requirements, emissions
requirements, and other suitable parameters. For example, during
low load or idle operation of power source 18, exhaust temperatures
and/or RPF temperatures may fall below a predetermined threshold
temperature for operation of RPF 23 and/or SCR system catalyst 31
(e.g., around 200 degrees C.). Where a sensor present in RPF 23 or
SCR system catalyst 31 indicates such a temperature condition,
controller 52 may limit or stop the flow of air and exhaust by
activating airflow control elements 25 and exhaust flow control
elements 27, thereby effecting a decrease in current emissions to
RPF 23 and/or SCR 31 and an increase in temperature of the
resulting exhaust gas. Upon allowing the flow of exhaust and air,
the increased temperature of the exhaust gas may allow RPF 23 and
SCR system catalyst 31 to continue operation.
[0047] Controller 52 may store data related to fuel to air ratios
for combustion in memory or other suitable storage location. Such
data may enable a determination of how many combustion cycles may
be executed within combustion chambers 30 before deactivating
airflow control elements 25 and exhaust flow control elements 27
such that a fresh air charge is allowed to enter and heated exhaust
gas to exit combustion chambers 30. Data may be experimentally
collected and based on engine size, engine rotations per minute
(RPM), engine load, among other things. Such data may be stored in
a lookup table within controller 52 for reference or data may be
calculated using algorithms stored within controller 52 and based
on similar parameters. For example, controller 52 may contain data
indicating that one combustion chamber of a particular engine
operating at 600 RPM may complete six combustion strokes with a
single air charge. Upon completion of six combustion strokes, or
upon other suitable conditions, controller 52 may cause a fresh air
charge to be introduced to combustion chambers 30 and exhaust gas
to flow from combustion chambers 30.
INDUSTRIAL APPLICABILITY
[0048] The disclosed systems and methods may be applicable to any
powered system that includes an exhaust gas producing power source,
such as an engine. The disclosed systems and methods may allow for
thermal management and emissions reduction from a power source. In
particular, the disclosed systems and methods may assist in
maintaining a predetermined exhaust-gas and catalyst temperature
during idle and low-load operation of the power source. Operation
of the disclosed systems and methods will now be explained.
[0049] Operation of combustion chambers 30 may be dependant on the
ratio of air to fuel-vapor that is supplied during operation. When
determining the air to fuel-vapor ratio, primary fuel as well as
other combustible materials in combustion chamber 30 (e.g.,
propane, etc.) may be included as fuel-vapor. The air to fuel-vapor
ratio is often expressed as a lambda value, which is derived from
the stoichiometric air to fuel-vapor ratio. The stoichiometric air
to fuel-vapor ratio is the chemically correct ratio for combustion
to take place. A stoichiometric air to fuel-vapor ratio may be
considered to be equivalent to a lambda value of 1.0.
[0050] Combustion chambers may operate at non-stoichiometric air to
fuel-vapor ratios. A combustion chamber with a lower air to
fuel-vapor ratio has a lambda less than 1.0 and is said to be rich.
A combustion chamber with a higher air to fuel-vapor ratio has a
lambda greater than 1.0 and is said to be lean.
[0051] Lambda may affect combustion chamber and exhaust
temperatures, emissions, and fuel efficiency. A lean-operating
combustion chamber may have higher combustion temperatures,
improved fuel efficiency, and residual air within a combustion
chamber following combustion as compared to a combustion chamber
operating under stoichiometric or rich conditions. However, as lean
operation may increase temperature, NOx production may also
increase creating a need to maintain the temperature of an SCR
system catalyst at predetermined level for efficient NOx
reduction.
[0052] During low load and idle of a power source, lambda values of
between 3.0 and 10.0 may be found within a combustion chamber
following a first intake stroke. Also during such operation,
exhaust gas temperatures may fall because a minimal amount of fuel
may be combusted to maintain idle and low load operation. Because
RPFs and SCR systems may provide maximum efficiency when maintained
at a predetermined temperature, a method for managing the thermal
output and exhaust emissions of an engine may be useful. In an
exemplary embodiment of the present disclosure, upon sensing a low
exhaust or catalyst temperature (e.g., RPF catalyst and/or SCR
catalyst) a controller may take appropriate action to manage
thermal characteristics of the power source to effect a temperature
rise in exhaust gas while controlling power source emissions.
[0053] FIG. 3 is a flowchart depicting one exemplary method for
operation of the disclosed systems and methods. FIG. 3 will be
discussed in the context of a single combustion chamber 30, but it
is to be understood that the operations described may apply to one
or more combustion chambers 30. In one embodiment, during a first
combustion cycle, an air charge may be provided to combustion
chamber 30 (step 300). The air charge may be provided during an
intake stroke of a piston mounted within combustion chamber 30.
During low load and/or idle operation, lambda values may be in the
range of 3.0 to 10.0. Following the provision of an air charge,
fuel may be provided to combustion chamber 30, for example via fuel
sources 38 (step 305). The fuel may then be combusted in combustion
chamber 30 and power derived from the resulting expansion of gases
(step 310). Following combustion, controller 52 may make a
determination as to whether there is sufficient air remaining in
combustion chamber 30 to execute another combustion stroke within
combustion chamber 30 (step 315). Such a determination may be based
on engine load, the number of combustion strokes since the last
fresh air charge, and/or size of combustion chamber 30, among other
things. Where controller 52 determines there is sufficient air
(step 315: yes), controller 52 may determine whether a temperature
or multiple temperatures are below a predetermined threshold
temperature (e.g., 200 degrees C.) (step 320). For example,
controller 52 may monitor temperatures of RPF 23 and SCR system
catalyst 31. Where controller 52 determines that the temperature or
temperatures are below a predetermined threshold (step 320: yes),
controller may determine whether airflow control elements 25 and
exhaust flow control elements 27 are currently activated and
substantially limiting or stopping the flow of air into combustion
chamber 30 and exhaust out of combustion chamber 30 (step 325). If
airflow control elements 25 and exhaust flow control elements 27
are currently activated (step 325: yes), fuel may once again be
provided to combustion chamber 30 (step 305) and the process
repeated. If airflow control elements 25 and exhaust flow control
elements 27 are not currently activated (step 325: no), controller
52 may cause the airflow control elements 25 and exhaust flow
control elements 27 to be activated (step 330) which may result in
a substantial limitation or stoppage of the flow of air to
combustion chamber 30 and exhaust gas from combustion chamber 30.
Fuel may then be provided to combustion chamber 30 (step 305).
[0054] Where controller 52 determines that insufficient air exists
within combustion chamber 30 (step 315: no) or that a temperature
or temperatures are above a predetermined threshold (step 320: no),
controller 52 may cause the deactivation of airflow control
elements 25 and exhaust flow control elements 27 (step 335)
allowing exhaust gas to flow from combustion chamber 30 into
exhaust manifold 28 and a fresh air charge to flow through intake
passage 24 into combustion chamber 30. A fluid connection between
exhaust manifold 28 and exhaust system 17 may then allow the
exhaust gas to be received by exhaust system 17. Exhaust system 17
may be configured to direct the exhaust gas flow through RPF 23
and/or SCR system catalyst 31 via a fluid connection (step 340).
Because the exhaust gas may be maintained at least above a minimum
temperature, RPF 23 may be enabled to filter and regenerate
particulate matter, while SCR system catalyst 31 may reduce NOx
emissions. This may result in the reduction efficiencies for
particulate matter and NOx emissions greater than 90 percent and
may meet federal regulations for year 2007 emissions.
[0055] Several advantages may be associated with the disclosed
systems and method for power source thermal management and
emissions reduction. For example, because a power source may
continue to operate all combustion chambers, the power source may
maintain balance and may be more responsive to sudden demands for
additional power. Maintenance of power source balance may result in
smoother low-load and idle operation. Also, there may be little or
no lag time during re-activation of combustion chambers because the
combustion chambers may continue to operate during thermal
management.
[0056] Moreover, by continuing to provide fuel to all combustion
chambers of the power source, more efficient combustion may be
achieved by limiting combustion of rich mixtures within the
combustion chambers. While lambda may decrease as additional
combustion strokes occur, lambda may not fall below a predetermined
value before additional air is introduced. This may lead to more
efficient lean combustion and therefore, to better fuel economy and
an overall reduction in hydrocarbon and other emissions.
[0057] Additionally, because combustion may continue in all
cylinders, more fuel may be burned than if a portion of the
cylinders were combusting additional fuel. More fuel being
combusted may then result in a greater potential temperature rise
of the resulting exhaust gas. This may, therefore, allow an RPF and
an SCR system to reach and maintain a minimum or optimal operating
temperature during low-load or idle operation in a decreased amount
of time.
[0058] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed system
and methods for power source thermal management and emissions
reduction. Other embodiments will be apparent to those skilled in
the art from consideration of the specification and practice of the
disclosed systems and methods for power source thermal management
and emissions reduction. It is intended that the specification and
examples be considered as exemplary only, with a true scope being
indicated by the following claims and their equivalents.
* * * * *