Engine performance management during a diesel particulate filter regeneration event

Various embodiments of an apparatus, system, and method are disclosed for managing regeneration event characteristics. For example, according to one embodiment, an apparatus for controlling the temperature of the output exhaust of an internal combustion engine for a regeneration event on a particulate matter filter includes a regeneration module, a turbocharger thermal management module, a fuel injection thermal management module, and an air intake thermal management module. The regeneration module determines a desired particulate matter filter inlet exhaust gas temperature for a regeneration event. The turbocharger thermal management module determines a variable geometry turbine (VGT) device position strategy. The fuel injection thermal management module determines a fuel injection strategy. The air intake thermal management module determines an intake throttle position strategy. The VGT device position strategy, the post-injection fuel injection strategy, and the intake throttle position strategy cooperatively achieve the desired particulate matter filter inlet exhaust gas temperature and maintain a fuel dilution level of the engine below a maximum fuel dilution level.

FIELD

This disclosure relates to controlling regeneration events on a diesel particulate filter (DPF) of an internal combustion engine system, and more particularly to the management of engine performance during a DPF regeneration event.

BACKGROUND

Emissions regulations for internal combustion engines have become more stringent over recent years. Environmental concerns have motivated the implementation of stricter emission requirements for internal combustion engines throughout much of the world. Governmental agencies, such as the Environmental Protection Agency (EPA) in the United States, carefully monitor the emission quality of engines and set acceptable emission standards, to which all engines must comply. Generally, emission requirements vary according to engine type. Emission tests for compression-ignition (diesel) engines typically monitor the release of diesel particulate matter (PM), nitrogen oxides (NOx), and unburned hydrocarbons (UHC). Catalytic converters implemented in an exhaust gas after-treatment system have been used to eliminate many of the pollutants present in exhaust gas. However, to remove diesel particulate matter, typically a diesel particulate filter (DPF) must be installed downstream from a catalytic converter, or in conjunction with a catalytic converter.

A common DPF comprises a porous ceramic matrix with parallel passageways through which exhaust gas passes. Particulate matter subsequently accumulates on the surface of the filter, creating a buildup which must eventually be removed to prevent obstruction of the exhaust gas flow. Common forms of particulate matter are ash and soot. Ash, typically a residue of burnt engine oil, is substantially incombustible and builds slowly within the filter. Soot, chiefly composed of carbon, results from incomplete combustion of fuel and generally comprises a large percentage of particulate matter buildup. Various conditions, including, but not limited to, engine operating conditions, mileage, driving style, terrain, etc., affect the rate at which particulate matter accumulates within a diesel particulate filter.

Accumulation of particulate matter typically causes backpressure within the exhaust system. Excessive backpressure on the engine can degrade engine performance. Particulate matter, in general, oxidizes in the presence of NO2at modest temperatures, or in the presence of oxygen at higher temperatures. If too much particulate matter has accumulated when oxidation begins, the oxidation rate may get high enough to cause an uncontrolled temperature excursion. The resulting heat can destroy the filter and damage surrounding structures. Recovery can be an expensive process.

To prevent potentially hazardous situations, accumulated particulate matter is commonly oxidized and removed in a controlled regeneration process before excessive levels have accumulated. To oxidize the accumulated particulate matter, exhaust gas temperatures generally must exceed the temperatures typically reached at the filter inlet. Consequently, additional methods to initiate regeneration of a diesel particulate filter may be used. In one method, a reactant, such as diesel fuel, is introduced into an exhaust after-treatment system to initiate oxidation of particulate buildup and to increase the temperature of the filter. A filter regeneration event occurs when substantial amounts of soot are consumed on the particulate filter.

A controlled regeneration can be initiated by the engine's control system when a predetermined amount of particulate has accumulated on the filter, when a predetermined time of engine operation has passed, or when the vehicle has driven a predetermined number of miles. Oxidation from oxygen (O2) generally occurs on the filter at temperatures above about 400° C., while oxidation from nitric oxides (NO2), sometimes referred to herein as noxidation, generally occurs at temperatures between about 250° C. and 400° C. Controlled regeneration typically consists of driving the filter temperature up to O2oxidation temperature levels for a predetermined time period such that oxidation of soot accumulated on the filter takes place.

A controlled regeneration can become uncontrolled if the oxidation process drives the temperature of the filter upwards more than is anticipated or desired, sometimes to the point beyond which the filter substrate material can absorb the heat, resulting in melting or other damage to the filter. Less damaging uncontrolled or spontaneous regeneration of the filter can also take place at noxidation temperatures, i.e., when the filter temperature falls between about 250° C. and 400° C. Such uncontrolled regeneration generally does not result in runaway temperatures, but can result in only partial regeneration of the soot on the filter. Partial regeneration can also occur when a controlled regeneration cannot continue because of a drop in temperature, exhaust gas flow rate, or the like. Partial regeneration and other factors can result in non-uniformity of soot distribution across the filter, resulting in soot load estimation inaccuracies and other problems.

The temperature of the particulate filter is dependent upon the temperature of the exhaust gas entering the particulate filter. Accordingly, the temperature of the exhaust must be carefully managed to ensure that a desired particulate filter inlet exhaust gas temperature is accurately and efficiently reached and maintained for a desired duration to achieve a controlled regeneration event that produces desired results.

Conventional systems use various strategies for managing the particulate filter inlet exhaust gas temperature. For example, some systems use a combination of air handling strategies, internal fuel dosing strategies, and external fuel dosing strategies. The air handling strategies include managing an air intake throttle to regulate the air-to-fuel ratio. Lower air-to-fuel ratios, e.g., richer air/fuel mixtures, typically produce a higher engine outlet exhaust gas temperature. Internal fuel dosing strategies include injecting additional fuel into the compression cylinders. Such in-cylinder injections include pre-injections or fuel injections occurring before a main fuel injection and post-injections or fuel injection occurring after a main fuel injection. Generally, post-injections include heat post-injections and non-heat post-injections. Heat post-injections are injections that participate along with the main fuel injection in the combustion event within the cylinder and occur relatively soon after the main fuel injection. Non-heat post injections are injections occur later in the expansion stroke compared to the heat post-injections and do not participate in the combustion event within the cylinder.

In internal combustions engines, unburned fuel can be forced by a combustion event to slip past, e.g., blow-by, the seals between the piston head and the wall of the compression cylinder. The unburned fuel that slips past the seals enters the crankshaft case chamber below the compression cylinders and intermixes with, e.g., dilutes, lubricating oil stored in the chamber. The fuel dilution level of an engine then is a measure of unburned fuel in the lubricating oil in the crankshaft case (often expressed as the percentage of unburned fuel in the fuel/oil mixture). Most engines generate normal amounts of fuel dilution (e.g., less than about 3%-5%), which often evaporates from the heat of the engine without negatively affecting the engine. However, when fuel dilution levels reach above-normal levels, the fuel does not burn off and may excessively thin the oil. Fuel diluted oil having excessively high fuel dilution levels can lower the lubricating properties of the oil, which can cause a drop in oil pressure and an increase in engine wear. Therefore, preventing the fuel dilution level of an engine from reaching above-normal amounts is an important part of proper engine maintenance and performance.

Although conventional regeneration fuel injection strategies may be adequate for controlling the temperature of exhaust generated by the engine, they often fail to maintain acceptable fuel dilution levels. For example, conventional systems with one heat post-injection participating in the combustion of fuel within the cylinder results in excessively high fuel dilution levels. Further, conventional regeneration fuel injection strategies result in more than typical amounts of fuel being injected into the compression cylinder. As discussed above, some of this fuel does not participate in the combustion event, i.e., the fuel is not combusted, and is not vaporized. With more fuel being injected into the compression cylinder than can be combusted and less vaporization of the fuel, the cylinders often contain excessive amounts of unburned and unvaporized fuel, which typically leads to increased fuel dilution levels.

Another known shortcoming of conventional engine systems having a particulate filter is the negative impact a regeneration event has on the performance of the engine, particularly during transient operations. Common non-additive engine controls strategies are designed primarily to achieve a desired engine outlet exhaust gas temperature without much attention being paid to the decrease in performance caused by such strategies. For example, some conventional engine control strategies that include multiple pre- and post-injections result in low combustion efficiencies due to the extra fuel in the combustion chamber. Reduced combustion efficiencies can cause a reduction in the performance, e.g., speed, torque, and fuel economy, of the engine.

Based on the foregoing, a need exists for an engine controls strategy that achieves targeted engine outlet exhaust gas temperatures for desired regeneration events while maintaining fuel dilution levels at or below an acceptable level for the engine and reducing negative effects on the performance of the engine during regeneration events conducted at various engine operating conditions.

SUMMARY

The subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available engine controls strategies for regeneration events. Accordingly, the subject matter of the present application has been developed to provide apparatus, systems, and methods for controlling the engine exhaust gas temperatures, fuel dilution levels, and engine performance during regeneration events that overcomes at least some shortcomings of the prior art engine controls strategies for regeneration events.

For example, according to one representative embodiment, an apparatus for controlling the temperature of the output exhaust of an internal combustion engine for a regeneration event on a particulate matter filter includes a regeneration module, a turbocharger thermal management module, a fuel injection thermal management module, and an air intake thermal management module. The regeneration module determines a desired particulate matter filter inlet exhaust gas temperature for a regeneration event. The turbocharger thermal management module determines a variable geometry turbine (VGT) device position strategy. The fuel injection thermal management module determines a fuel injection strategy. The air intake throttle thermal management module determines an intake throttle position strategy. The VGT device position strategy, the post-injection fuel injection strategy, and the intake throttle position strategy cooperatively achieve the desired particulate matter filter inlet exhaust gas temperature and maintain a fuel dilution level of the engine below a maximum fuel dilution level.

In some implementations, the apparatus also includes an exhaust gas recirculation (EGR) thermal management module that determines an exhaust throttle valve position strategy. In such implementations, the VGT device position strategy, the fuel injection strategy, the intake throttle position strategy, and the exhaust throttle valve position strategy cooperatively achieve the desired particulate matter filter inlet exhaust gas temperature. In specific instances, the internal combustion engine is operable in a low speed operating range, a high speed operating range, and a transition operating range between the low and high speed operating ranges. In such instances, the exhaust throttle valve position strategy includes closing the exhaust throttle valve when operating in the low speed operating range, and opening the exhaust throttle valve when operating in the high speed operating range.

According to certain embodiments, the fuel injection thermal management module includes a fuel dilution module configured to determine a maximum fuel dilution level of the engine, wherein the fuel injection strategy is configured to achieve an actual fuel dilution level below or equal to the maximum fuel dilution level.

In some implementations, the internal combustion engine is operable in a low speed operating range, a high speed operating range, and a transition operating range between the low and high speed operating ranges. The VGT device position strategy can include closing the VGT device when operating in the low speed operating range, opening the VGT device when operating in the high speed operating range, and moving the VGT device between the closed and open position in the transition operating range when the engine is transitioning between the low speed operating range and the high speed operating range. The engine is also operable in an intermediate speed operating range overlapping at least a portion of the low speed operating range, the entire transition operating range, and at least a portion high speed operating range. The fuel injection strategy can include at least one heat post-injection. In some instances, the fuel injection strategy also includes at least one non-heat post-injection when operating in the low and intermediate speed operating range.

According to another embodiment, a method is disclosed for controlling the temperature of the inlet exhaust of a particulate matter filter for a regeneration event on the particulate matter filter. The particulate matter filter is coupled in exhaust receiving communication with an internal combustion engine. The method includes determining a desired particulate matter filter inlet exhaust gas temperature. Additionally, the method includes determining and implementing a VGT device position strategy for achieving the desired particulate matter filter inlet exhaust gas temperature. If the VGT device position strategy does not achieve an actual particulate matter filter inlet exhaust gas temperature approximately equal to or greater than the desired particulate matter filter inlet exhaust gas temperature, the method includes determining and implementing a multiple post-injection strategy for achieving the desired particulate matter filter inlet exhaust gas temperature. If, however, the multiple-post injection strategy does not achieve an actual particulate matter filter inlet exhaust gas temperature approximately equal to or greater than the desired particulate matter filter inlet exhaust gas temperature, the method includes determining and implementing an intake throttle position strategy for achieving the desired particulate matter filter inlet exhaust gas temperature.

According to some implementations, the method further includes determining and implementing an exhaust throttle valve position strategy for achieving the desired particulate matter filter inlet exhaust gas temperature if the VGT device position strategy does not achieve an actual particulate matter filter inlet exhaust gas temperature approximately equal to or greater than the desired particulate matter filter inlet exhaust gas temperature. The multiple post-injection strategy for achieving the desired particulate matter filter inlet exhaust gas temperature is determined and implemented if the if the exhaust throttle valve position strategy does not achieve an actual particulate matter filter inlet exhaust gas temperature approximately equal to or greater than the desired particulate matter filter inlet exhaust gas temperature.

In certain implementations, the method includes determining whether a smooth transition limit of the VGT device has been met. If the smooth transition limit of the VGT device has been met, the method further includes determining and implementing a new VGT device position strategy for achieving the desired particulate matter filter inlet exhaust gas temperature and avoiding an un-smooth transition of the VGT device.

In yet certain implementations, the method includes determining whether the exhaust flow rate meets or exceeds an exhaust flow rate lower limit after implementation of the intake throttle position. If the exhaust flow rate does not meet or exceed the exhaust flow rate lower limit, the method further includes determining and implementing a new intake throttle position strategy for achieving the desired particulate matter filter inlet exhaust gas temperature and meeting or exceeding the exhaust flow rate lower limit.

According to some implementations, the action of determining the multiple post-injection strategy includes determining a desired exhaust gas temperature increase from heat post-injections and determining whether one heat post-injection is sufficient to achieve the desired exhaust gas temperature increase. If one heat post-injection is not sufficient, the method includes determining whether two heat post-injections are sufficient to achieve the desired exhaust gas temperature increase.

After implementing the multiple post-injection strategy of the method, the method further includes determining whether an actual fuel dilution level of the engine exceeds a predetermined maximum fuel dilution level of the engine. If the actual fuel dilution level of the engine exceeds the predetermined maximum fuel dilution level of the engine, the method includes determining and implementing a new multiple post-injection strategy for achieving the desired particulate matter filter inlet exhaust gas temperature and reducing or maintaining the actual fuel dilution level of the engine to a level at or below the maximum fuel dilution level.

In some implementations, the action of determining the multiple post-injection strategy can include determining a desired filter inlet exhaust gas temperature increase from non-heat post-injections and determining whether one non-heat post-injection is sufficient to achieve the desired filter inlet exhaust gas temperature increase. If one non-heat post-injection is sufficient, the method includes setting the number of non-heat post-injections of the multiple post-injection strategy to one non-heat post-injection. If one non-heat post-injection is not sufficient, the method includes determining whether two non-heat post-injections are sufficient to achieve the desired exhaust gas temperature increase. If two non-heat post-injections are sufficient, the method includes setting the number of non-heat post-injections of the multiple post-injection strategy to two non-heat post-injections. But, if two non-heat post-injections are not sufficient, the method includes setting the number of non-heat post-injections of the multiple post-injection strategy to three non-heat post-injections.

According to another embodiment, a method for controlling the temperature of the inlet exhaust of a particulate matter filter coupled to an internal combustion engine for a regeneration event on the particulate matter filter includes determining a desired particulate matter filter inlet exhaust gas temperature. The method also includes determining a VGT device position strategy configurable to increase the filter inlet exhaust gas temperature during a regeneration event, determining an exhaust throttle valve position strategy configurable to increase the filter inlet exhaust gas temperature during a regeneration event, determining a multiple post-injection strategy configurable to increase the filter inlet exhaust gas temperature during a regeneration event, and determining an intake throttle position strategy configurable to increase the filter inlet exhaust gas temperature during a regeneration event. The method further includes cooperatively implementing the VGT device position strategy, exhaust throttle valve position strategy, multiple post-injection strategy, and intake throttle position strategy to increase the filter inlet exhaust gas temperature to the desired particulate matter filter inlet exhaust gas temperature.

According to another embodiment, an internal combustion engine system includes an internal combustion engine generating an engine outlet exhaust, a particulate matter filter in exhaust receiving communication with the internal combustion engine, and a controller. The controller includes an engine conditions module configured to determine operating conditions of the engine and a regeneration module configured to determine a desired particulate matter filter inlet exhaust gas temperature for conducting a regeneration event on the particulate matter filter. The controller further includes an engine system thermal management module configured to determine a VGT device actuation strategy for increasing the temperature of exhaust entering the particulate matter filter a first desired amount, an exhaust throttle actuation strategy for increasing the temperature of exhaust entering the particulate matter filter a second desired amount, a regeneration fuel injection strategy for increasing the temperature of exhaust entering the particulate matter filter a third desired amount, and an air intake throttle actuation strategy for increasing the temperature of exhaust entering the particulate matter filter a fourth desired amount. The first, second, third, and fourth desired temperature increase amounts are combinable to increase the temperature of exhaust entering the particulate matter filter to a temperature at or above the desired particulate matter filter inlet exhaust gas temperature.

The first, second, third, and fourth desired temperature increase amounts can each be any of various temperature increase amounts ranging from zero up to any desired amount. A desired temperature increase amount can be set to zero if it is undesirable for a particular component, e.g., VGT device, exhaust throttle, post-injections, and intake throttle, to participate in the exhaust gas temperature increase process.

In some implementations, the engine system thermal management module is configured to determine a fuel dilution threshold level and the internal combustion engine is operable in a low fuel dilution mode when the fuel dilution level of the engine exceeds the fuel dilution threshold level. The internal combustion engine is operable in the low fuel dilution mode by setting the third desired temperature increase amount to zero.

In certain instances of the internal combustion engine system, the first desired temperature increase amount is greater than the third desired temperature increase amount. For example, at certain engine operating conditions, the fuel amounts from non-heat post-injections are limited to controlling only the engine outlet hydrocarbon level and fuel dilution level. In other instances, the third desired temperature increase amount is greater than the first desired temperature increase amount. For example, at certain other engine operating conditions, VGT position is controlled such that the exhaust flow rate meets the lower limit requirement and the turbine inlet exhaust pressure meets an upper limit.

According to some implementations of the internal combustion engine system, the engine system thermal management module is configured to determine a fuel dilution threshold level and the regeneration fuel injection strategy is configured to maintain the fuel dilution level of the engine at a level not greater than the fuel dilution threshold level.

Further, in some implementations of the internal combustion engine system, the controller includes a predetermined map that has empirically obtained engine outlet exhaust gas temperatures, particulate matter filter inlet exhaust gas temperatures, and fuel dilution levels for given VGT device positions, exhaust throttle positions, regeneration post-injections, and air intake throttle positions. In such implementations, the determination of the VGT strategy, exhaust throttle actuation strategy, regeneration fuel injection strategy, and air intake actuation strategy by the engine system thermal management module can include accessing data from the predetermined map.

Furthermore, the described features, advantages, and characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the subject matter may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments. These features and advantages will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter.

DETAILED DESCRIPTION

Furthermore, the described features, structures, or characteristics of the subject matter described herein may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of controls, structures, algorithms, programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments of the subject matter. One skilled in the relevant art will recognize, however, that the subject matter may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the disclosed subject matter.

FIG. 1depicts one exemplary embodiment of an internal combustion engine system, such as a diesel engine system100, in accordance with the present invention. As illustrated, the engine system100includes a diesel engine110, a controller130, a fuel delivery system131, a turbocharger system155, an exhaust gas recirculation (EGR) system157, and an exhaust gas aftertreatment system159.

The engine110includes an air inlet112, intake manifold114, and exhaust manifold116. The air inlet112is vented to the atmosphere, enabling air to enter the engine110. The air inlet112is connected to an inlet of the intake manifold114. The intake manifold114includes an outlet operatively coupled to combustion chambers111of the engine110. The air from the atmosphere is combined with fuel to power, or otherwise, operate the engine110. The fuel is delivered into the combustion chambers111by the fuel delivery system131. The fuel delivery system131includes a fuel tank180for storing the fuel and a fuel pump (not shown) for delivery the fuel to a common rail133. From the common rail, the fuel is injected into combustion chambers111through one of several fuel injectors135. The timing and dosage of fuel into the combustion chambers111is controlled by the controller130via electronic communication lines (shown as dashed lines inFIG. 1). Combustion of the fuel produces exhaust gas that is operatively vented to the exhaust manifold116.

The quantity of air entering the intake manifold114and thus the combustion chambers111is regulated by an intake throttle115operatively coupled to an accelerator pedal (not shown). The position of the intake throttle115and the quantity of air entering the intake manifold114corresponds at least partially to the position of the accelerator pedal. The intake throttle115also is in electrical communication with the controller130and controllable by the controller. The controller130is operable to regulate the quantity of air entering the intake manifold114independent of the position of the accelerator pedal.

From the exhaust manifold116, the exhaust gas flows into at least one of three systems, i.e., the turbocharger system155, the EGR system157, and the exhaust gas aftertreatment system159. For example, based at least partially on the operating conditions of the engine, a portion of the exhaust gas can be directed into the turbocharger system155, a portion of the exhaust gas can be directed into the EGR system157, and a portion of the exhaust gas can be directed into the exhaust aftertreatment system159. The relative portions of exhaust gas entering the respective systems155,157,159are controlled by the controller130. Generally, the controller130determines the relative portions of exhaust gas that should enter the respective systems and commands valves, e.g., valves132,134, to allow a portion of the exhaust corresponding to the determined portions to enter the respective systems.

The turbocharger system155includes a turbocharger turbine118, turbocharger compressor120, and the turbocharger bypass valve132. The turbocharger bypass valve132is selectively operable to regulate the flow of exhaust gas into the turbocharger turbine118. The exhaust gas entering the turbine118causes the turbine to drive the compressor120. When driven by the turbine118, the compressor120compresses engine intake air before directing it to the intake manifold114.

In certain implementations, the turbocharger turbine118is a variable geometry turbine (VGT) having a VGT device119such as is commonly known in the art. The VGT device119can be a series of movable vanes for controlling the flow of exhaust hitting the blades of the turbine. For example, at low engine speeds, the exhaust velocity is insufficient to effectively spin the turbine. Accordingly, at low engine speeds, the vanes can be moved into a relatively closed position such that the spaces between the vanes are relatively small. As the exhaust passes through the small spaces, it accelerates and is redirected to contact the turbine blades at a specific angle for optimum or fully enhanced rotation of the blades. In contrast, at high engine speeds, the exhaust velocity is sufficient to effectively spin the turbine. Accordingly, at high engine speeds, the vanes can be moved into a relatively open position such that the spaces between the vanes are relatively large. As the exhaust passes through the large spaces, its velocity remains relatively constant and experiences minimal redirection such that the blades of the turbine experience a less enhanced rotation. The positions of the vanes are adjusted via an actuator in electrical communication with the controller130such that the controller130can control the positions of the vanes.

The EGR system157includes an EGR cooler122, an EGR valve134, and an EGR cooler bypass valve154. The EGR valve134is selectively controlled by the controller130to regulate the flow of exhaust entering the EGR system157from the exhaust manifold, and thus indirectly regulating the flow of exhaust entering the aftertreatment system159. When the EGR valve134is at least partially open, at least a portion of the engine exhaust enters the EGR system157and is re-circulated into the combustion chambers111of the engine110to be combusted with air from the air intake112. Prior to entering the combustion chambers111, the EGR exhaust gas can be passed through the EGR cooler122to cool the exhaust gas in order to facilitate increased engine air inlet density. The EGR cooler bypass valve154is operatively controlled by the controller130to regulate the amount of EGR exhaust passing through the EGR cooler122and the amount of EGR exhaust gas bypassing the EGR cooler122via an EGR bypass line152.

In addition to the VGT device119and the EGR valve134, the flow rate of exhaust entering the exhaust aftertreatment system159can be regulated by an exhaust throttle137positioned within the exhaust stream between the catalytic component140and the turbocharger system155. Like the VGT device119, the exhaust throttle137is actuatable between a closed position and an open position. The closed position corresponds with a minimum space through which exhaust gas can pass and the open position corresponds with a maximum space through which exhaust gas can pass. As the space through which the exhaust flows is reduced, the flow rate of the exhaust is reduced. Therefore, as the exhaust throttle137moves from the open position to the closed position, the flow rate of exhaust entering the aftertreatment system159decreases. Similarly, as the exhaust throttle137moves from the closed position to the open position, the flow rate of exhaust entering the aftertreatment system159increases.

The valve positions of the VGT device119and exhaust throttle137affect the load on the engine and thus the temperature of the exhaust gas. For example, when the VGT device119is in a closed position, a backpressure is created in the exhaust manifold. In order to overcome the backpressure in the exhaust, the engine must increase its pumping work, e.g., load. The increased pumping work results in an increase in the engine outlet exhaust gas temperature. Similar to the VGT device119, the more closed the exhaust throttle137valve position, the more backpressure created in the exhaust manifold, and the more pumping work performed by the engine. Accordingly, in certain instances, the temperature of the engine outlet exhaust can be increased by closing at least one of the VGT device119and exhaust throttle137. For example, in some implementations, the VGT device119and exhaust throttle137can be controlled independent of each other to increase the engine outlet exhaust gas temperature. Alternatively, the VGT device119and exhaust throttle137can be dependently or cooperatively controlled to provide more precise control of the engine outlet exhaust gas temperature.

The exhaust aftertreatment system159includes a catalytic component140, a particulate filter150downstream of the catalytic component140, and a regeneration mechanism. The exhaust gas may pass through one or more catalytic components, such as catalytic component140, to reduce the number of pollutants in the exhaust gas prior to the gas entering the particulate filter. In certain implementations, the catalytic component140is a conventional diesel oxidation catalyst. The pollutants, e.g., carbon monoxide, particulate matter, and hydrocarbons, are reduced in an oxidation process within the catalytic component140. Typically, for oxidation of the pollutants to occur, the catalyst of the catalytic component140much be at a temperature within a predetermined range, e.g., between about 250° C. and about 300° C. in some instances. The temperature of the catalytic component140is regulated by controlling the engine outlet exhaust gas temperature. The exothermic oxidation process for reducing the pollutants in the exhaust also causes the temperature of the exhaust gas to increase such that during an oxidation event on the catalytic component140, the catalytic component outlet exhaust gas temperature is greater than the catalytic component outlet exhaust gas inlet temperature. In some implementations, fuel is added to the exhaust prior to entering the catalytic component140. The added fuel raises the temperature of the exhaust exiting the catalytic component140by participating in the exothermic oxidation reaction. The amount of fuel added to the exhaust gas is proportional to the increase in the exhaust gas temperature due to the catalytic component140, i.e., the catalytic component exhaust gas temperature increase.

The particulate filter150filters particulate matter from the exhaust gas stream before venting to the atmosphere. The particulate matter can build on the face of the particulate filter catalyst. Particulate matter produced by the engine110comprises ash and soot. Soot accumulates much faster than ash, such that, in many cases, particularly when the filter has been in operation for a relatively short period, an estimate of the rate of total particulate accumulation can be satisfactorily generated by estimating the rate of soot accumulation, treating the ash accumulation rate as negligible. Accordingly, the particulate filter150requires periodic regeneration to remove the particulate matter from the filter. The regeneration mechanism160regenerates the filter150, with the controller130establishing a regeneration vector and directing the regeneration mechanism160to regenerate the filter150in a regeneration profile corresponding to the regeneration vector, as further detailed below.

Various sensors, such as temperature sensors124, pressure sensors126, fuel sensor128, exhaust gas flow sensors165, and the like, may be strategically disposed throughout the engine system100and may be in communication with the controller130to monitor operating conditions. In one embodiment, the fuel sensor128senses the amount of fuel consumed by the engine, and the exhaust gas flow sensors165sense the rate at which exhaust gas is flowing at the particulate filter150.

Engine operating conditions can be ascertained from any of the sensors or from the controller130's commands to the engine regarding the fraction of exhaust gas recirculation, injection timing, and the like. In one embodiment, information is gathered regarding, for example, fuel rate, engine speed, engine load, the timing at which fuel injection timing is advanced or retarded (SOI, or start of injection), time passed, fraction of exhaust gas recirculation, driving conditions, whether and when regenerations have occurred and the rate such regenerations have removed particulate matter, exhaust flow rate, the amount of O2and NO2in the exhaust, filter temperature, exhaust gas pressure, filter particulate load amount and uniformity, etc.

The engine110will produce soot and ash at a rate that will vary according to the type of engine; for example, whether it is an 11-liter or 15-liter diesel engine. Additionally, the rate of particulate production will vary according to engine operating conditions such as fuel rate, EGR fraction, and SOI timing. Other factors may also bear on the particulate production rate, some depending heavily on the engine platform being considered, with others closer to being platform-independent.

Although the engine system100shown inFIG. 1uses an internal fuel injection approach to controlling the exhaust gas temperature for regeneration events, in other embodiments, an external fuel injection approach can be used in conjunction with the non-additive fuel injection strategies described herein. The external fuel injection approach can be the same as or similar to the approach described in U.S. Pat. No. 7,263,825, which is incorporated herein by reference.

FIG. 2depicts a control system200according to one representative embodiment. The control system200includes the controller130, the intake throttle115, the VGT device119, the exhaust throttle137, sensors280(e.g., sensors124,126,128,165), a regeneration device290(e.g., the regeneration mechanism160), and the fuel injectors135. The controller130includes an input module240, a conditions module250, a regeneration module260, an output module270, and an engine system thermal management module275.

As is known in the art, the controller130and components may comprise processor, memory, and interface modules that may be fabricated of semiconductor gates on one or more semiconductor substrates. Each semiconductor substrate may be packaged in one or more semiconductor devices mounted on circuit cards. Connections between the modules may be through semiconductor metal layers, substrate-to-substrate wiring, or circuit card traces or wires connecting the semiconductor devices.

The sensors280are configured to determine a plurality of conditions within the engine system100, including temperature, pressure, exhaust gas flow rate, etc. The regeneration device290is configured to regenerate the filter150at the direction of the controller150. The input module240is configured to input the conditions sensed by the sensors280and provide corresponding inputs to the regeneration module260, which creates a regeneration vector according to the inputs. The conditions module250is configured to gather information regarding current operating conditions430of the engine system100, based on the conditions sensed by the sensors280and/or other inputs including commands issued to system components by the controller130.

The output module270is configured to direct the regeneration device290to regenerate the filter150according to regeneration instructions generated by the regeneration module260and the current conditions determined by the conditions module250. The output module270also is configured to direct the fuel injectors135to inject fuel into the compression chambers of the engine110according to a fuel injection strategy determined by the engine system thermal management module275. Further, the output module270is configured to direct the intake throttle115to regulate the flow rate of intake air into the intake manifold114according to a desired intake air flow rate determined by the engine system thermal management module275. The output module270also is configured to command the VGT device119into a desired configuration determined by the engine system thermal management module275. Further, the output module270is configured to direct the exhaust throttle137to regulate the flow rate of exhaust entering the exhaust aftertreatment system159according to a desired aftertreatment system exhaust flow rate determined by the engine system thermal management module275.

FIG. 3is a schematic block diagram illustrating another embodiment of the control system200ofFIG. 2. The controller130is depicted as comprising a processor module305, memory module310, and interface module315. The processor module305, memory module310, and interface module315may be fabricated of semiconductor gates on one or more semiconductor substrates. Each semiconductor substrate may be packaged in one or more semiconductor devices mounted on circuit cards. Connections between the processor module305, the memory module310, and the interface module315may be through semiconductor metal layers, substrate to substrate wiring, or circuit card traces or wires connecting the semiconductor devices.

The memory module310stores software instructions and data comprising one or more software processes. The processor module305executes the software processes as is known to those skilled in the art. In one embodiment, the processor module305executes one or more software processes carried out by the conditions module250, regeneration module260, and engine system thermal management module275ofFIG. 2.

The processor module305may communicate with external devices and sensors, such as the sensors280, the regeneration device290, the fuel injectors135, the intake throttle115, the VGT device119, and the exhaust throttle137, ofFIG. 2through the interface module315. For example, the sensors280may comprise a pressure sensor126(FIG. 1), with the sensors280communicating an analog signal representing a pressure value to the interface module315. The interface module315may periodically convert the analog signal to a digital value and communicate the digital value to the processor module305.

The interface module315may also receive one or more digital signals through a dedicated digital interface, a serial digital bus communicating a plurality of digital values, or the like. For example, the sensors280may comprise the air-flow sensor156ofFIG. 1and communicate a digital air flow value to the interface module315. The interface module315may periodically communicate the digital air flow value to the processor module305. In one embodiment, the interface module315executes one or more communication processes carried out by the input module240and output module270ofFIG. 2.

The processor module305may store digital values such as the pressure value and the air flow value in the memory module310. In addition, the processor module305may employ the digital values in one or more calculations including calculations carried out by the conditions module250and regeneration module260. The processor module305may also control one or more devices, such as the fuel injectors135, intake throttle,115, VGT device119, exhaust throttle137, and regeneration device290, through the interface module315.

The regeneration module260is configured to generate a regeneration command, e.g., regeneration instructions, representing a request to initiate a regeneration event on the particulate filter150and the desired characteristics of the regeneration event. In other words, the regeneration module260commands the regeneration device when to perform a regeneration event, how long to perform the regeneration event, the rate of regeneration during the regeneration event, and determines the desired temperature of the exhaust entering the particulate filter (e.g., a desired filter inlet exhaust gas temperature425) necessary to achieve the desired characteristics of the regeneration event.

Based on the desired filter inlet exhaust gas temperature425(i.e., desired catalytic component or DOC outlet exhaust gas temperature), the regeneration module260is configured to determine a desired temperature of the exhaust exiting the exhaust manifold116(e.g., a desired engine outlet exhaust gas temperature435). In embodiments where the engine system100includes a catalytic component140, the filter inlet exhaust gas temperature is equal to the engine outlet exhaust gas temperature plus the exhaust gas temperature increase produced by the catalytic component140. The desired filter inlet exhaust gas temperature425then is equal to the desired engine outlet exhaust gas temperature435plus a desired catalytic component exhaust gas temperature increase. Accordingly, the desired filter exhaust gas temperature425is achievable by controlling at least one of the engine outlet exhaust gas temperature and the catalytic component exhaust gas temperature increase. Further, the determination of the desired engine outlet exhaust gas temperature435of the engine includes an anticipated drop in the temperature due to the turbine118. Therefore, the regeneration module260compensates for the changes in exhaust gas temperature due to operation of the turbine118in its determination of the desired engine outlet exhaust gas temperature435.

Generally, the regeneration command and associated regeneration event characteristics are dependent upon the accumulation and/or distribution of particulate matter on the filter150. Additionally, the regeneration command and event characteristics are dependent upon any of various other parameters, such as, for example, the operating conditions of the engine, the availability of future regeneration opportunities, the operating trends of the engine, etc. In certain embodiments, the regeneration module260generates the regeneration command by utilizing the particulate filter regeneration principles and strategies described in U.S. patent application Ser. Nos. 11/301,808 (filed Dec. 13, 2005), 11/301,998 (filed Dec. 13, 2005), 11/301,701 (filed Dec. 13, 2005), 11/227,857 (filed Sep. 15, 2005), 11/227,403 (filed Sep. 15, 2005), 11/301,693 (filed Dec. 13, 2005), 11/227,828 (filed Sep. 15, 2005), 11/226,972 (filed Sep. 15, 2005), 11/227,060 (filed Sep. 15, 2005), and 12/039,614 (filed Feb. 28, 2008), and U.S. Pat. Nos. 7,231,291; 7,263,825; and 7,188,512. Each of the above-listed patents and patent applications are incorporated herein by reference.

The regeneration module260communicates the regeneration command, or at least certain portions of the regeneration command, to the engine system thermal management module275. In one embodiment, as shown inFIG. 4, the regeneration module260communicates the desired filter inlet exhaust gas temperature425and desired engine outlet exhaust gas temperature435of the regeneration command to the engine system thermal management module275.

The engine system thermal management module275includes a turbocharger thermal management module405, an exhaust throttle thermal management module410, a fuel injection thermal management module415, and an air intake thermal management module420. Generally, the engine system thermal management module275determines a thermal management strategy for each cycle of the engine110. Each thermal management strategy represents the operating parameters of one or more components of the engine system estimated to achieve the desired filter inlet exhaust gas temperature, maintain the dilution level below a maximum dilution level threshold, and attain a desired engine outlet performance for each engine cycle during regeneration events. Further, based at least partially on the desired filter inlet exhaust gas temperature425and desired engine outlet exhaust gas temperature435received from the regeneration module260, the engine system thermal management module275determines a thermal management strategy for achieving a desired engine outlet exhaust gas temperature and, if necessary, a desired catalytic component exhaust gas temperature increase that together provide the desired filter inlet exhaust gas temperature425.

The thermal management strategy is represented by one or more component commands generated by the engine system thermal management module275and communicated to the respective components. In the illustrated embodiment, the commands includes at least one of a VGT command450, an exhaust throttle command455, a fuel injection command460, and an intake throttle command465. Generally, the commands450,455,460,465are configured to achieve the desired engine outlet exhaust gas temperature and any desired catalytic component exhaust gas temperature increase.

The VGT command450is originally generated from the turbocharger thermal management module405. The VGT command450represents a VGT device position strategy regarding the position of the VGT device119relative to the speed and torque of the engine. In a first engine operating range570, e.g., at relatively lower operating speeds, the VGT command450can request a closed position of the VGT device119(seeFIG. 5). With the VGT device119closed, the engine outlet exhaust gas temperature is increased due to the increased energy consumed to expel exhaust gas from the engine cylinders, which increases the pumping work performed by the engine. In a second engine operating range580, e.g., at relatively higher engine speeds and lower torques, the VGT command450can request an open position of the VGT device119(seeFIG. 5). With the VGT device119open during operation in the second engine operating range580, the air-to-fuel ratio is reduced because less intake air is flowing into the combustion chamber. With less air in the combustion chamber, the temperature of the resultant exhaust gas is increased. Accordingly, the VGT device119can be commanded to close and open to increase the temperature of the exhaust exiting the engine in order to meet the desired filter exhaust gas temperature425for a regeneration event.

Similar to the turbocharger thermal management module405, the exhaust throttle thermal management module410is configured to generate the exhaust throttle command455. The exhaust throttle command455represents an exhaust throttle strategy regarding the position of the exhaust throttle137valve relative to the speed and torque of the engine. The position of the exhaust throttle137valve affects the temperature of the exhaust gas generated by the engine much in the same way as the VGT device119. For example, when the exhaust throttle137valve is closed during operation within the first engine operating range570, the engine outlet exhaust gas temperature is increased.

In certain implementations, the turbocharger and exhaust throttle thermal management modules405,410are in electrical communication and work together to generate a VGT command450and exhaust throttle command455that cooperatively produce an engine outlet exhaust gas temperature corresponding to the desired engine outlet exhaust gas temperature435. For example, the VGT device119can be opened or closed and the exhaust throttle137valve can be positionable in any of various positions between the open and closed positions to provide any of various engine outlet exhaust gas temperature increases.

The VGT device119also is positionable in any of various positions between the open and closed positions. However, when changing between the open and closed positions during transient operating conditions of the engine, slow transient response, torque transparency, and VGT actuator reliability problems can occur. Therefore, during transient operations, the VGT device119may be an unreliable and problematic exhaust gas temperature control device for a narrow operating speed transition range when the VGT device is changing between the closed and open position. In other words, with regards to changes in the engine outlet exhaust gas temperature, the transition between the first and second engine operating ranges570,580, and a third transition operating range590intermediate the first and second engine operating ranges may be rough.

For operating speed and torque combinations within a fourth intermediate engine operating range595(e.g., an operating range leading up to, during, and trailing the third transition operating range590), a regeneration fuel injection strategy developed by the fuel injection thermal management module415can be provided to smooth the engine outlet exhaust gas temperature changes during transient engine operating conditions. In other words, a fuel injection strategy can be used in conjunction with the VGT device position strategy and/or the exhaust throttle position strategy to provide better control of the engine outlet exhaust gas temperature during transient and even steady-state engine operations. As shown inFIG. 5, the regeneration fuel injection strategy can be implemented when the engine is operating in the fourth intermediate engine operating range595.

Based at least partially on the desired filter inlet exhaust gas temperature425and desired engine outlet exhaust gas temperature435received from the regeneration module260and the operating conditions430of the engine received from the conditions module250, the fuel injection thermal management module415generates the fuel injection command460to the fuel injectors. The fuel injectors135respond to the fuel injection command by injecting fuel into the compression chambers according to the fuel injection command. The fuel injection command includes instructions for performing a multiple-injection event corresponding to a desired exhaust gas temperature increase and fuel dilution level limit for each cycle of the engine. In certain instances, the multiple-injection event is represented by the relative timing of a plurality of fuel injections and the quantity or dosage of fuel injected in each of the plurality of fuel injections. Generally, the multiple-injection event is configured to promote fuel spray vaporization by injecting smaller amounts of fuel into the cylinder. More fuel spray vaporization results in less fuel spray impinging on the cylinder wall, which translates into a reduced likelihood of fuel blow-by and a reduced level of fuel dilution compared to conventional thermal management strategies. Additionally, a multiple-injection event extends the combustion process to later crank angle positions compared to a single-injection event. Extending the combustion process to later crank angle positions within a misfire limit provides increased engine exhaust gas temperature using smaller amounts of fuel compared to a single-injection event.

Referring toFIG. 6, the fuel injection thermal management module415includes a fuel dilution module610and a fuel injection strategy module620. The fuel dilution module610is configured to determine an acceptable, e.g., maximum, fuel dilution level for the engine110. The acceptable fuel dilution level for a given engine can be experimentally obtained and integrated into a fuel dilution map comparing fuel dilution values against engine operating conditions and/or cycles. Based at least partially on one or more of the above factors, the fuel dilution module610determines the acceptable fuel dilution level of the engine110.

The fuel injection strategy module620is configured to determine a regeneration fuel injection strategy and generate the fuel injection command460for communication to the fuel injectors135. The regeneration fuel injection strategy is at least partially dependent upon the acceptable fuel dilution level determined by the fuel dilution module610. More specifically, the fuel injection strategy module620determines a regeneration fuel injection strategy that will, in conjunction with the VGT device strategy and EGR valve strategy in some embodiments, achieve the desired engine outlet exhaust gas temperature and overall engine performance without exceeding the acceptable fuel dilution level. The regeneration fuel injection strategy is dependent largely upon the operating conditions of the engine110. For example, the regeneration fuel injection strategy for the engine110when operating at lower speed conditions can be a first regeneration fuel injection strategy, and the regeneration fuel injection strategy for the engine when operating at higher speed conditions can be a second regeneration fuel injection strategy different than the first regeneration fuel injection strategy.

The regeneration fuel injection strategies are determined by the fuel injection strategy module620on a per cycle basis. In other words, the fuel injection strategy module620determines a regeneration fuel injection strategy for each combustion cycle of the engine during a regeneration event initiated by the regeneration module260and when the engine in operating in the fourth intermediate operating range595. The regeneration event typically includes a period for ramping up the temperature of the particulate filter150, actual regeneration on the particulate filter at predetermined filter temperatures, and any ramping down of the temperature of the particulate filter. In certain implementations, the fuel injection strategies can be determined as described in U.S. patent application Ser. No. 12/111,831, entitled THERMAL MANAGEMENT OF DIESEL PARTICULATE FILTER REGENERATION EVENTS, and filed on Apr. 29, 2008, which is incorporated herein by reference.

Referring toFIG. 7, and according to one embodiment, each regeneration fuel injection strategy700includes fuel dosage and timing information for a main fuel injection710and at least a first heat post-injection720. In some implementations, each regeneration strategy700can also include a second heat post-injection730. The main fuel injection710is the primary injection of the combustion event in the cylinder. The main fuel injection710occurs whether a regeneration event is occurring or not. Each of the first and second heat post-injections720,730also participate in the combustion event within the cylinder. More specifically, the first and second heat post-injections720,730occur close enough to the main fuel injection710that they are involved in the combustion event driven by the main fuel injection710. Accordingly, as used herein, heat injections are injections where the injected fuel participates in the combustion event.

In some implementations, the regeneration fuel injection strategy700includes one or more non-heat post-injections. The illustrated regeneration fuel injection strategy includes two non-heat post-injections740,750. Because the non-heat post-injections740,750occur well after the main fuel injection710, they do not participate in the combustion event within the cylinder. Generally, the non-heat post-injections740,750are included in the strategy700to enrich the exhaust with hydrocarbons and increase the temperature of the exhaust exiting the catalytic component140(i.e., increase the catalytic component exhaust gas temperature). Accordingly, as used herein, non-heat injections are injections where the injected fuel does not participate in the combustion event.

The regeneration fuel injection strategy700also includes a pilot fuel injection760occurring just prior to the main fuel injection710. The pilot fuel injection760drives a smaller combustion event preceding the main combustion event driven by the main fuel injection710. The smaller combustion event promotes a gradual increase in the temperature within the compression cylinder prior to the rapid temperature increase associated with the main combustion event. Generally, the smaller combustion event reduces potential negative effects of the sudden temperature increase associated with main combustion events, e.g., engine knock and rattles.

As shown inFIG. 7, the timing and the dosage of the fuel injections710,720,730,740,750,760can vary. Typically, the timing of a fuel injection is represented by the angle of the crank when the fuel is injected into the compression cylinder. Accordingly the timing of a scheduled fuel injection is represented by the angle of the crank when the fuel is scheduled to be injected into the compression cylinder. Further, because a fuel injection event requires a period of time to inject the required dosage of fuel, for convenience, the timing of a fuel injection is associated with the start of the fuel injection event. InFIG. 7, the timing of the fuel injections are compared against a single combustion cycle timeline from a top-dead center (TDC) position770of the crank (i.e., when the piston reaches its uppermost point within the cylinder), to a bottom-dead center (BDC) position780of the crank (i.e., when the piston reaches its lowermost point within the cylinder), and back to the TDC position. The TDC position770is associated with a crank angle of zero-degrees and the BDC position780is associated with a crank angle of 180-degrees. As shown, the main fuel injection occurs at TDC, the first heat post-injection720occurs at a first crank angle CA1relative to the TDC position770, and the second heat post-injection730occurs at a second crank angle CA2relative to the first crank angle CA1and a third crank angle CA3relative to the TDC position. The first non-heat post-injection740occurs at a fourth crank angle CA4relative to the TDC position770and the second non-heat post-injection750occurs at a fifth crank angle CA5relative to the fourth crank angle CA4and a sixth crank angle CA6relative to the TDC position.

In certain implementations, the first crank angle CA1is an angle between about 8-degrees and about 30-degrees, the second crank angle CA2is greater than approximately 5-degrees, the third crank angle CA3is between about 30-degrees and about 63-degrees, the fourth crank angle CA4is between about 150-degrees and about 170-degrees, the fifth crank angle CA5is greater than about 2-degrees, and the sixth crank angle CA6is between about 160-degrees and about 180-degrees.

The dosage of the fuel injections710,720,730,740,750,760consists of the fuel flow rate and the fuel injection duration. In other words, the duel dosage can be varied by varying either one or more of the fuel flow rate and fuel injection duration. Generally, better performance is achieved by increasing the flow rate and decreasing the fuel injection duration. However, increasing the desired fuel flow rate typically requires an increase in the capability requirements of the fuel injection system. Accordingly, the fuel flow rate and fuel injection duration are dependent upon the fuel injection system.

A regeneration fuel injection strategy700having two heat post-injections720,730, as opposed to one heat post-injection, provides several advantages. For example, two heat post-injections allow more flexibility in achieving higher exhaust gas temperatures while maintaining acceptable fuel dilution levels. Referring to the chart800ofFIG. 8, which represents empirical data gathered during testing of a representative engine, the exhaust gas temperatures achieved by a single heat-post injection strategy810and a dual heat post-injection strategy820are comparable. For example, the temperature achieved with the dual heat post-injection strategy820is nearly the same as the temperature achieved with the single heat post-injection strategy. Nevertheless, the fuel dilution encountered when using the dual heat post-injection strategy820is significantly lower than the fuel dilution encountered when using the single heat post-injection strategy810(e.g., 2.02% versus 6.8%, or only about 30% of the fuel dilution encountered with the single heat post-injection strategy) in order to achieve the same engine outlet exhaust gas temperature. Based on the foregoing, dual heat post-injection strategies provide much lower fuel dilution levels at similar exhaust gas temperatures than single heat post-injection strategies. Therefore, utilizing dual heat post-injection strategies as described herein facilitates large or small changes in the engine exhaust gas temperature without significantly affecting the fuel dilution levels.

The exhaust gas temperatures, e.g., the engine outlet exhaust gas temperature and filter inlet exhaust gas temperature, achieved with a dual heat post-injection strategy can be increased, without significantly increasing the fuel dilution levels, by adding one or more non-heat post-injections, such as injections740,750ofFIG. 7. For example, as shown inFIG. 8, even though the filter inlet exhaust gas temperature achieved using the single and triple post-injection strategies810,830are about the same, two heat post-injections and one non-heat post-injection (e.g., the triple post injection strategy830) results in an engine outlet exhaust temperature that is higher than the target engine outlet exhaust gas temperature840and a 64% lower fuel dilution level than using the single heat post-injection strategy

The chart800shows exemplary target engine outlet exhaust gas temperature840and target particulate filter inlet exhaust gas temperature850. As shown, the representative single and triple post-injection strategies810,830both achieve the target filter inlet exhaust gas temperature850, but the triple post-injection strategy830does so while producing a significantly lower fuel dilution level. Moreover, while the single, dual, and triple post-injection strategies810,820,830achieve the target engine outlet exhaust gas temperature840, the triple post-injection strategy830achieves the target engine outlet exhaust gas temperature and target filter inlet exhaust gas temperature with a much lower fuel dilution level, which can promote flexibility in determining fuel injection strategies in view of accomplishing other desired engine operating parameters, such as higher fuel economy and more efficient hydrocarbon conversion in the catalyst component140.

Regeneration fuel injection strategies having two heat post-injections, such as the regeneration fuel injection strategy700shown inFIG. 7, are capable of achieving the same or similar engine exhaust gas temperatures as single heat post-injection strategies, but with lower fuel dilution levels than single heat post-injection strategies for some engine operating conditions. Moreover, regeneration fuel injection strategies employing two heat post-injections are capable of achieving higher engine outlet exhaust gas temperatures than single heat post-injections for other operating conditions. In such operating conditions, single heat post-injections often are not able to achieve a target engine outlet exhaust gas temperature, while the dual heat post-injections are able to achieve the target engine outlet exhaust gas temperature. Further, regeneration fuel injection strategies employing two heat post-injections and one or more non-heat post-injections are capable of achieving higher filter inlet exhaust gas temperatures than dual heat post-injection strategies without non-heat post-injections, but with similar dilution levels as dual heat post-injection strategies without non-heat post-injections.

In addition to VGT device, exhaust throttle, and fuel injection strategies, an air intake throttle strategy can be used to control the engine outlet exhaust gas temperature, fuel dilution level, and engine performance. The air intake throttle strategy is generated by the air intake thermal management module420and includes information on the desired position of the air intake throttle relative to the operating range in which the engine is operating. The air intake throttle strategy is represented by the intake throttle command465, which commands the air intake throttle115to actuate into a requested position to allow a desired amount of air to flow into the intake manifold114.

Like the VGT device119and exhaust throttle134, the position of the air intake throttle115, and thus the amount of air entering the intake manifold114, affects the temperature of the exhaust gas generated by the engine. For example, the less air let through the throttle at low engine speeds, generally the higher the engine outlet exhaust gas temperature. The air intake throttle115is primarily controlled according to the position of the accelerator pedal. However, the position of the air intake throttle115is further controlled by the controller130to adjust the temperature of the engine outlet exhaust gas. Generally, the air intake throttle strategy involves selectively reducing the air intake flow via actuation of the throttle115within the first engine operating range570.

In certain implementations, when operating in the first and second engine operating ranges570,580during a regeneration event, the turbocharger management module405, exhaust throttle thermal management module410, and air intake thermal management module420are in electrical communication and work together to generate a VGT command450, exhaust throttle command455, and intake throttle command465that cooperatively produce an engine outlet exhaust gas temperature corresponding to the desired filter exhaust gas temperature425. For example, the VGT device119can be open or closed, the exhaust throttle can be positionable in any of various positions between the open and closed positions, and the air intake throttle115can be positionable in any of various positions to provide any of various engine outlet exhaust gas temperature increases. Each of the VGT, exhaust throttle, and air intake strategies are configurable to increase the engine outlet temperature a respective amount. The respective exhaust gas temperature increase amounts are combinable with the normal engine outlet exhaust gas temperature to achieve the desired filter inlet exhaust gas temperature.

When the engine is operating in the fourth intermediate engine operating range595during a regeneration event, the fuel injection thermal management module415is in electrical communication and works together with the turbocharger, exhaust throttle, and air intake thermal management modules405,410,420according to a first exhaust gas temperature control strategy to generate a VGT command450, an exhaust throttle command455, an intake throttle command465, and a fuel injection command460that cooperatively produce an engine outlet exhaust gas temperature corresponding to the desired filter inlet exhaust gas temperature. The commands450,455,465,460are dependent upon the desired filter inlet exhaust gas temperature and a smooth transition limit of the VGT device119. The smooth transition limit of the VGT device119is the limitation of VGT change rate due to the engine speed and/or torque changes in which adjustment of the VGT device119may yield unpredictable behavior. As discussed above, the regeneration fuel injection strategy represented by the fuel injection command460facilitates a smooth transition between the first and second engine operating ranges570,580during transient engine operating conditions. In certain embodiments, such as during operation in the fourth intermediate engine operating range595, each of the VGT, exhaust throttle, fuel injection, and air intake strategies are configurable to increase the engine outlet temperature a respective amount within the limitations of the VGT position change rate, and the fuel injection strategy is further configurable to increase the catalytic component gas temperature a desired amount. The respective exhaust gas temperature increase amounts and the catalytic component temperature increase amount are combinable with the normal engine outlet exhaust gas temperature to achieve the desired filter inlet exhaust gas temperature.

Referring toFIG. 9, in one embodiment, a method900for implementing the first exhaust gas temperature control strategy during a regeneration event includes determining905a desired filter exhaust gas temperature. The desired filter inlet exhaust gas temperature can be determined by the regeneration module260as discussed above. The method900proceeds by determining910whether the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425. The actual filter inlet exhaust gas temperature can be interpreted from an exhaust sensor positioned proximate the inlet to the particulate filter150. If the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425as determined at910, then the method900ends. However, if the actual filter inlet exhaust gas temperature is less than the desire filter inlet exhaust gas temperature425, then the method900proceeds by determining and implementing915VGT device119and/or exhaust throttle134position strategies. The strategies are represented by a VGT command450and an exhaust throttle command455, respectively, as discussed above with each command corresponding to a desired position of the VGT device and exhaust throttle valve, respectively.

In certain instances, VGT device119and exhaust throttle137positions for the various engine operating conditions are predetermined based on engine development mapping data, which can be stored in the memory module310. Alternatively, the VGT device119can be adjusted to achieve a desired engine outlet exhaust gas temperature within the VGT smooth transition limit. If the desired engine outlet exhaust gas temperature is not achievable solely by adjusting the VGT device position, then the exhaust throttle position may be adjusted. In the illustrated embodiment, the engine system100includes both a VGT device and an exhaust throttle. However, in other embodiments, the engine system may include either a VGT device or an exhaust throttle.

After the position of the VGT device119is adjusted, it is determined at920whether the new VGT device position results in the smooth transition limit of the VGT device being met. If the smooth transition limit of the VGT device119is met, the method900adjusts the position of the VGT device such that the smooth transition limit is not met and proceeds to determine whether the actual filter exhaust gas temperature is greater than or the same as the desired filter exhaust gas temperature425at930. If the smooth transition limit of the VGT device119is not met at920, then the method900determines whether the actual filter inlet exhaust gas temperature is greater than or the same as the desired filter inlet exhaust gas temperature425at930. If at930it is determined that the actual filter inlet exhaust gas temperature is indeed greater than or the same as the desired filter inlet exhaust gas temperature425, the method900ends.

However, if the actual filter inlet exhaust gas temperature is not greater than or the same as the desired filter inlet exhaust gas temperature425as determined at930, then the method900continues to determine and implement935a post-injection strategy such as described above. After the post-injection strategy is implemented, the method900then determines whether the actual filter inlet exhaust gas temperature is greater than or the same as the desired filter inlet exhaust gas temperature425as determined at940. If the actual filter inlet exhaust gas temperature is greater than or the same as the desired filter inlet exhaust gas temperature425as determined at940, the method ends. However, if the actual filter inlet exhaust gas temperature is not greater than or the same as the desired filter inlet exhaust gas temperature as determined at940, then the method continues to determine and implement an intake throttle position strategy945if available. The intake throttle position strategy945is represented by an intake throttle command465corresponding to a desired position of the intake throttle valve115.

After the intake throttle position strategy is implemented at945, the method900determines whether the engine outlet exhaust flow rate is greater than or equal to an exhaust flow rate lower limit. The flow rate of exhaust must be higher than a predetermined exhaust flow rate lower limit to effectuate the desired temperature distribution within the particulate filter150and avoid damaging or melting the filter due to uncontrolled regeneration caused when the temperature of the filter exceeds a predetermined maximum temperature capacity of the filter substrate material. If the exhaust flow rate is less than the exhaust flow rate lower limit, then the method returns to event945to determine and implement a new intake throttle position strategy including an increase in the commanded air intake necessary to achieve or exceed the exhaust flow rate lower limit. Once the exhaust flow rate meets or exceeds the exhaust flow rate lower limit, the method900proceeds to determine whether the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425at955.

If it is determined at955that the actual filter inlet exhaust gas temperature is lower than the desired filter inlet exhaust gas temperature425, then the method900returns to event915to determine and implement a new VGT device and/or exhaust throttle position strategy, and the method900continues as described above.

In other implementations, if it is determined at955that the actual filter inlet exhaust gas temperature is lower than the desired filter inlet exhaust gas temperature425, the method can continue in one of various ways depending on which exhaust gas temperature modifier is preferred. A determination of the preferred exhaust gas temperature modifier can be based on any of various factors, such as, for example, fuel economy, power output, driving conditions, and engine operating conditions.

For example, if using the VGT device119or exhaust throttle134to increase the exhaust gas temperature is preferred, the method900can continue from a negative output at955to a VGT device and/or exhaust throttle position continuous loop beginning at event915. The VGT device and/or exhaust throttle position continuous loop can include events915,920,925, and930. If at930, the actual filter inlet exhaust gas temperature is not greater than or equal to the desired filter inlet exhaust gas temperature425, then instead of continuing to event935, the method900returns to event915. The continuous loop continues until the actual filter inlet exhaust gas temperature determined at930is greater than or equal to the desired filter inlet exhaust gas temperature425.

Alternatively, although not shown inFIG. 9, if using multiple post-injections to increase the exhaust gas temperature is preferred, the method900can continue from a negative output at955to a multiple post-injection continuous loop beginning at event935. The multiple post-injection continuous loop can include events935and940. If at940, the actual filter inlet exhaust gas temperature is not greater than or equal to the desired filter inlet exhaust gas temperature425, then instead of continuing to event945, the method900returns to event930. The continuous loop continues until the actual filter inlet exhaust gas temperature determined at940is greater than or equal to the desired filter inlet exhaust gas temperature425.

Further, although not shown inFIG. 9, if using the position of the air intake throttle115to increase the exhaust gas temperature is preferred, the method900can continue from a negative output at955to an air intake continuous loop beginning at event945. The air intake continuous loop can include events945,950, and955. If at955, the actual filter inlet exhaust gas temperature is not greater than or equal to the desired filter inlet exhaust gas temperature425, then instead of continuing to event915, the method900returns to event945. The continuous loop continues until the actual filter inlet exhaust gas temperature determined at955is greater than or equal to the desired filter inlet exhaust gas temperature425.

In some embodiments where the fuel dilution level of the engine is a concern, the turbocharger, exhaust throttle, air intake, and fuel injection thermal management modules405,410,420,415cooperatively operate according to a first exhaust gas temperature and fuel dilution strategy. According to the first exhaust gas temperature and fuel dilution strategy, the VGT command450, exhaust throttle valve command455, intake throttle command465, and fuel injection command460are dependent upon the desired filter inlet exhaust gas temperature425, a smooth transition limit of the VGT device119, and a fuel dilution limit of the engine. The generated commands450,455,465,460are configured to cooperatively produce an engine outlet exhaust gas temperature corresponding to the desired filter inlet exhaust gas temperature425and a fuel dilution level below the fuel dilution limit.

According to one implementation, the methods900,1000,1100(methods1000,1100described below) can be modified to operate the engine in a low fuel dilution mode if the fuel dilution monitor detects a fuel dilution level above a predetermined high fuel dilution limit. For example, if the fuel dilution monitor detects a fuel dilution level above the high fuel dilution limit, the method900can be modified to remove or skip event935such that following event930, the method900proceeds directly to event945. In this manner, the potential increase in fuel dilution levels associated with post-injections can be eliminated to maintain the actual fuel dilution at a level below the high fuel dilution limit.

Referring toFIG. 10, one embodiment of a method1000achieving the determining and implementing a post-injection strategy event935of method900includes determining1005a desired exhaust gas temperature increase. The method1000continues by determining1010whether one heat post-injection will be sufficient for achieving the desired exhaust gas temperature increase. If one heat post-injection is sufficient, the method1000continues by determining1025the quantity or dosage of fuel and the timing of the post-injection. If one heat post-injection is insufficient, the method continues by determining1015whether two heat post-injections will be sufficient for achieving the desired exhaust gas temperature increase. If two heat post-injections are sufficient, the method1000continues by determining1020the quantity or dosage of fuel and the timing of the second post-injection, and determining1025the quantity or dosage of duel and the timing of the first post-injection. However, if two heat post-injections are not sufficient, the method1000returns to event905of method900at1017. The method900attempts to increase the temperature of the engine outlet exhaust gas at events905and915. Therefore, when the method900reaches event935and the method1000is again implemented, the desired exhaust gas temperature increase may be less such that the two, or perhaps one, heat post-injections may now be sufficient for achieving the desired exhaust gas temperature increase.

If one or two heat post-injections are sufficient as determined at910,915and after the injection characteristics of the first and/or second heat post-injections are determined at1020,1025, the method1000continues by determining1030if the actual fuel dilution level is greater than a maximum fuel dilution level of the engine. If the actual fuel dilution level is greater than the maximum fuel dilution level, the method proceeds to event1040. If it was previously determined at event1010that one heat post-injection was sufficient, then the method1000returns to event1025to modify the injection characteristics of the first heat post-injection only. If it was previously determined at events1010and1015that two heat post-injections were sufficient, then the method1000returns to event1020to modify the injection characteristics of the second heat post-injection and then to event1025to modify the injection characteristics of the first heat post-injection. If the actual fuel dilution level is less than or equal to the maximum fuel dilution level, then the method1000continues by determining1035whether the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425. If the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425, then the method1000ends. However, if the actual filter inlet exhaust gas temperature is less than the desired filter inlet exhaust gas temperature425, then the method returns to event1020or event1025depending on whether one or heat two post-injections were determined to be sufficient.

In certain implementations, the method1000does not include event1035such that once the actual fuel dilution level is less than or equal to the maximum fuel dilution level as determined at1030, the method1000ends and the method800proceeds to event840.

Often, the catalytic component140may demand a greater increase in the engine outlet exhaust gas temperature to achieve proper oxidation on the catalytic component140as well as to ensure that the temperature of the exhaust entering the particulate filter is sufficient to conduct a regeneration event. Therefore, in certain implementations, the multiple post-injection strategy determined and implemented at835includes a heat post-injection strategy such as described in method1000as well as a non-heat post-injection strategy, such as shown in method1100ofFIG. 11. The non-heat post-injection strategy, e.g., method1100, can be performed following completion of the heat post-injection strategy, e.g., method1000.

Referring toFIG. 11, method1100includes determining1110a desired temperature increase in the engine exhaust, which can include an increase in the engine outlet exhaust gas and an increase in the catalytic component outlet gas. As discussed above, such temperature increases are necessary to achieve an engine outlet exhaust gas temperature that will result in a desired catalytic component inlet exhaust gas temperature corresponding to the desired filter inlet exhaust gas temperature425. Based on the determined desired temperature increase, the method1100includes determining1120the total fuel quantity necessary to achieve the desired temperature increase. The method1100then continues by determining1130whether one non-heat post-injection is sufficient to achieve the temperature increase. If one non-heat post-injection is not sufficient, the method1100includes determining1140whether two non-heat post-injections are sufficient to achieve the temperature increase. If one non-heat post-injection is sufficient, then the method1100determines1160the fuel quantity and timing of the non-heat post-injection. If two non-heat post-injections are sufficient, the method1100determines1150fuel quantity and timing of the second of the two non-heat post-injections and then determines1160the first of the two non-heat post-injections. If neither one nor two non-heat post-injections are sufficient, the method1100proceeds to determine1170the fuel quantity and timing of a third non-heat post-injection, and then continues to determine the quantity and timing of the second and first non-heat post-injections at1150,1160, respectively. The timing and dosage of the first, second, and third non-heat post-injections can be determined according to a fuel injection control algorithm based on engine mapping data obtained during engine development, and accessible by or stored on the fuel injection strategy module620. The dosage of the non-heat post-injections can also be determined based on the energy balance and the temperature difference between the engine outlet and the particulate matter filter inlet.

Following event1160, the method1100includes determining1175whether the actual fuel dilution level is greater than a maximum fuel dilution level of the engine. If the actual fuel dilution level is greater than the maximum fuel dilution level, then the method proceeds to determine1185whether one non-heat post-injection was sufficient. If event1185is affirmatively answered, the method1100returns to event1160, and if event1185is negatively answered, the method proceeds to determine1190whether two non-heat post-injections were sufficient. If event1190is affirmatively answered, the method1100returns to event1150, and if event1190is negatively answered, the method returns to event1170.

If the actual fuel dilution level is lower than or equal to the maximum fuel dilution level, then the method proceeds to determine1180whether the actual filter inlet exhaust gas temperature is greater than or equal to the desired filter inlet exhaust gas temperature425and whether the actual catalytic component inlet exhaust gas temperature is greater than or equal to the desired catalytic component inlet exhaust gas temperature. If event1180is answered affirmatively, then the method1100ends. However, if the event1180is answered negatively, then the method1100returns to event1185.

If event1185is affirmatively answered, the method1100returns to event1160, and if event1185is negatively answered, the method proceeds to determine1190whether two non-heat post-injections were sufficient. If event1190is affirmatively answered, the method1100returns to event1150, and if event1190is negatively answered, the method returns to event1170.

Actual fuel dilution levels from methods1000,1100can be interpreted from on-line fuel dilution sensors or monitors coupled to the engine110. Further, as mentioned above, the actual engine outlet, filter input, and catalytic component inlet exhaust gas temperatures can be interpreted from temperature sensors. In the event one or more of the fuel dilution and temperature sensors are unavailable, predicted values for the actual fuel dilution and actual engine outlet and filter inlet exhaust gas temperatures can be obtained from predetermined look-up tables or maps based on the operating conditions of the engine system100. Further, in some implementations of method1100, if an on-line fuel dilution sensor is unavailable, the quantity of each non-heat post-injection can be determined based on a predetermined maximum allowable non-heat post-injection fuel quantity. The predetermined maximum allowable non-heat post-injection fuel quantity can be a function of the timing of the non-heat post-injection, such as whether the post-injection falls within a predetermined timing window.

The schematic flow chart diagrams and method schematic diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of representative embodiments. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the methods illustrated in the schematic diagrams. Additionally, the format and symbols employed are provided to explain the logical steps of the schematic diagrams and are understood not to limit the scope of the methods illustrated by the diagrams. Although various arrow types and line types may be employed in the schematic diagrams, they are understood not to limit the scope of the corresponding methods. Indeed, some arrows or other connectors may be used to indicate only the logical flow of a method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of a depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.