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.

Description

TECHNICAL FIELD

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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

FIG. 1 provides a pictorial representation of an exemplary machine having multiple systems and components that may cooperate to accomplish a task;

FIG. 2 schematically illustrates a power source capable of implementing the disclosed systems and methods for thermal management and emissions reduction; and

FIG. 3 is a flowchart depicting one exemplary method for operation of the disclosed systems and methods.

DETAILED DESCRIPTION

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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, CO₂, 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.

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.

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.

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.

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.

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.

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.

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.

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.

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+O₂→CO₂   (1)

NO₂+C→NO→+CO₂   (2)

NO+O₂→NOx   (3)

Carbon present in particulate matter may be combusted in the presence of oxygen to produce CO₂ 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 NO₂ to form NO and CO₂. The resulting NO may then react with available O₂ to re-form NO₂ as illustrated by equation 3. While NO₂ is a NOx variant, the resultant NO₂ 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.

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.

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.

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+O₂ oxygenated HC   (4)

NOx+oxygenated HC+O₂→N₂+CO₂+H₂O   (5)

SCR system catalyst 31 may catalyze the reduction of NOx to N₂ 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 (N₂) 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).

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.

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

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.