GB2578906A

GB2578906A - System and method for control of combustion parameters based on SCR catalyst conditions

Info

Publication number: GB2578906A
Application number: GB1818484.6A
Authority: GB
Inventors: J McLaren Stephen; Sagener Semih; T Simpson Julian; J Stuart Benjamin
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2018-11-13
Filing date: 2018-11-13
Publication date: 2020-06-03
Anticipated expiration: 2038-11-13
Also published as: GB2578906B; GB201818484D0

Abstract

A method comprises receiving information indicative of the storage state of a selective catalytic reduction (SCR) catalyst (50, fig 1) and determining a difference between the ammonia storage capacity of the SCR catalyst and a target ammonia storage state. The method also comprises receiving information indicative of a space velocity through the SCR catalyst. If the difference between the ammonia storage capacity of the SCR catalyst and a target ammonia storage state exceeds a difference threshold, and the space velocity exceeds a space velocity threshold, an engine (18, fig 1) is commanded to operate according to low nitrous oxide (NOx) parameters. If the difference is at or below the difference threshold and the space velocity is less than or equal to the space velocity threshold, the engine is commanded to operate according to high NOx combustion parameters. The method is carried out by a system comprising a controller (26, fig 2) or an apparatus comprising a selective catalytic reduction storage circuit (114, fig 2) and an engine operation circuit (126, fig 2).

Description

SYSTEM AND METHOD FOR CONTROL OF COMBUSTION

PARAMETERS BASED ON SCR CATALYST CONDITIONS

TECHNICAL FIELD

[0001] The present disclosure relates to exhaust aftertreatment systems. More particularly, the present disclosure relates to systems and methods for determining engine combustion parameters based on conditions of a selective catalytic reduction catalyst.

BACKGROUND

[0002] 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. Consequently, the use of exhaust aftertreatment systems on engines to reduce emissions is increasing.

[0003] Exhaust aftertreatment system components can function at different efficiencies based on factors such as temperature, failure of components, and degradation of components of the exhaust aftertreatment system. For example, a selective catalytic reduction catalyst can perform differently at different temperatures. As another example, a selective catalytic reduction catalyst deployed in the exhaust aftertreatment system may degrade or become dirty. Since the failure or degradation of components can have adverse consequences on the performance and emission-reduction capability of the exhaust aftertreatment system, the detection of failed or degraded components is desirable.

SUMMARY

[0004] One embodiment relates to a system. The system includes a controller structured to receive information indicative of a storage capacity of a selective catalytic reduction (SCR) catalyst, determine a difference between the ammonia storage capacity of the SCR catalyst and a target ammonia storage state, compare the difference to a difference threshold, receive information indicative of a space velocity through the SCR catalyst, and compare the information indicative of the space velocity through the SCR catalyst to a space velocity threshold. In response to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold, the controller is structured to command an engine to operate according to low nitrous oxide (NOx) combustion parameters. In response to the difference being at or below the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold, the controller is structured to command the engine to operate according to high NOx combustion parameters.

[0005] Commanding the engine to operate according to the high NOx combustion parameters may generate exhaust having a higher NOx concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.

[0006] The low NOx combustion parameters may include at least a first plurality of fuel pressure values and a first plurality of fuel injection values. The high NOx combustion parameters may include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.

[0007] The space velocity may be indicative of an amount of time the exhaust is exposed to the SCR catalyst.

[0008] The controller may be further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.

[0009] The target ammonia storage state may be based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof [0010] One embodiment relates to an apparatus. The apparatus includes a selective catalytic reduction (SCR) storage circuit, a SCR space velocity circuit, and an engine operation circuit. The SCR storage circuit is structured to receive information indicative of a storage capacity of a SCR catalyst, to determine a difference between the information indicative of the storage capacity of the SCR catalyst and a target ammonia storage state, and compare the difference to a difference threshold. The SCR space velocity circuit is structured to receive information indicative of a space velocity through the SCR catalyst and compare the information indicative of the space velocity through the SCR catalyst to a space velocity threshold. The engine operation circuit is structured to command an engine to operate according to low NOx combustion parameters or high NOx combustion parameters based on the comparison.

[0011] The engine operation circuit may be structured to command the engine to operate according to the low NOx combustion parameters in response to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold.

[0012] The engine operation circuit may be structured to command the engine to operate according to the high NOx combustion parameters in response to the difference being less than or equal to the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold.

[0013] Commanding the engine to operate according to the high NOx combustion parameters may generate exhaust having a higher nitrous oxide (NOx) concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.

[0014] The low NOx combustion parameters may include at least a first plurality of fuel pressure values and a first plurality of fuel injection values. The high NOx combustion parameters may include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.

[0015] The space velocity may be indicative of an amount of time the exhaust is exposed to the SCR catalyst.

100161 The controller may be further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.

[0017] The target ammonia storage state may be based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof [0018] One embodiment relates to a method. The method includes receiving information indicative of a storage capacity of a selective catalytic reduction (SCR) catalyst, receiving information indicative of a space velocity through the SCR catalyst, determining a difference between the information indicative of the storage capacity of the SCR catalyst to a target ammonia storage state, comparing the difference to a difference threshold, and comparing the information indicative of the space velocity through the SCR catalyst to a space velocity threshold. The method further includes commanding an engine to operate according to low NOx combustion parameters in response to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold. The method further includes commanding the engine to operate according to high NOx combustion parameters in response to the difference being at or below the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold.

[0019] Commanding the engine to operate according to the high NOx combustion parameters may generate exhaust having a higher nitrous oxide (N0x) concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.

[0020] The low NOx combustion parameters may include at least a first plurality of fuel pressure values and a first plurality of fuel injection values. The high NOx combustion parameters may include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.

[0021] The space velocity may be indicative of an amount of time the exhaust is exposed to the SCR catalyst.

[0022] The controller may be further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.

[0023] The target ammonia storage state may be based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof [0024] These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0025] FIG. I is a schematic diagram of a vehicle including an exhaust aftertreatment system with a controller, according to an example embodiment.

[0026] FIG. 2 is a schematic representation of a controller of the vehicle of FIG. 1, according to an example embodiment.

[0027] FIG. 3 illustrates a flow diagram of a method for controlling engine combustion parameters based on selective catalytic reduction (SCR) system parameters, according to an example embodiment.

[0028] FIG. 4 illustrates a boxplot of an amount of NOx in the exhaust gas leaving the engine for a conventional engine and an engine operating according to the method of FIG. 3, according to an example embodiment.

[0029] FIG. 5 illustrates a boxplot of an amount of NOx in the exhaust gas leaving the vehicle for the conventional engine and the engine operating according to the method of FIG. 3, according to an example embodiment.

[0030] FIG. 6 illustrates a boxplot of brake specific fuel consumption (BSFC) for the conventional engine and the engine operating according to the method of FIG. 3, according to an example embodiment.

[0031] FIG. 7 illustrates emissions test data for a cumulative vehicle outlet NOx concentration, a space velocity of the exhaust gas through the SCR catalyst, and a SCR catalyst temperature, according to an example embodiment.

[0032] FIG. 8 illustrates emissions test data for ammonia storage levels of the SCR catalyst, according to an example embodiment.

DETAILED DESCRIPTION

[0033] Following below are more detailed descriptions of various concepts related to, and embodiments of methods, apparatuses, and systems for determining engine combustion parameters based on operating conditions (e.g. temperature and ammonia storage status) of a selective catalytic reduction (SCR) catalyst of a SCR system of a vehicle. The various concepts introduced herein below may be implemented in any number of ways, as the concepts described are not limited to any particular manner of embodiment. Examples of specific embodiments and applications are provided primarily for illustrative purposes.

[00341 Conventional vehicles include engines in exhaust-receiving communication with selective catalytic reduction (SCR) systems for converting nitrous oxides (NOx) in the exhaust gas into less harmful products. The engine can be operated according to different combustion parameters based on operating conditions of the vehicle to change an amount of power output by the engine and/or to change an amount of NOx in the exhaust gas. For example, the combustion parameters of the engine can be changed based on a temperature of the SCR system so that the SCR can convert substantially all of the NOx in the exhaust stream into less harmful compounds. However, the dynamics of the SCR catalyst are complex and depend on more than the temperature of the SCR catalyst. Accordingly, conventional vehicles that determine combustion parameters based only on the temperature of the SCR catalyst may oversize the volume of the SCR system and/or operate the engines according to fuel consumption parameters that result in higher fuel consumption.

[0035] Referring to the figures generally, the various embodiments disclosed herein relate to systems, apparatuses, and methods for dynamically assessing operating conditions of a SCR catalyst and controlling engine combustion parameters based on the operating conditions of the SCR catalyst.

[0036] As shown in FIG. 1, a vehicle 10 includes an engine system 14 including an engine 18 in exhaust gas-receiving communication with an exhaust gas processor or exhaust aftertreatment system 22, a controller 26, and an operator input/output (I/O) device 30 is depicted, according to an example embodiment. According to one embodiment and as shown, the engine 18 is structured as a compression-ignition internal combustion (IC) engine that utilizes diesel fuel. Within the internal combustion engine 18, air from the atmosphere is combined with fuel, and combusted, to power the engine 18. Combustion of the fuel and air in the compression chambers of the engine 18 produces exhaust gas that is operatively vented to an intake manifold 34 and to the exhaust aftertreatment system 22.

[0037] The engine 18 can be operated to generate exhaust gas having high levels of NOx or to generate exhaust gas having low levels of NOx. Operating the engine 18 to generate exhaust gas having high NOx exhaust gas reduces a brake specific fuel consumption (BSFC) of the engine 18, meaning that the engine 18 generates more power per unit of fuel consumed. The BSFC is a measure of the efficiency of the engine and is determined by dividing a rate of fuel consumption of the engine by an amount of power produced by the engine. For example, combustion parameters that maximize efficiency have high cylinder pressure and high temperature when engine pistons are at the top dead center position at the beginning of the expansion stroke, so that the working fluid (e.g., air, an air-fuel mixture, etc.) is expanded over the maximum possible difference in volumes and the most energy can be extracted from it. NOx production is greater at higher pressure and higher temperature. For combustion parameters that yield low NOx production, the pressure and temperature rise occurs after top dead center position, to reduce the peak cylinder pressure and temperature. This means that the working fluid is expanded over a smaller range of volumes and less of the energy can be extracted, so low NOx combustion parameters are less efficient and the engine produces less power per unit of fuel consumed.

[0038] Returning to FIG. 1, the exhaust aftertreatment system 22 includes a selective catalytic reduction (SCR) system 46 with an SCR catalyst 50. In some embodiments, the aftertreatment system 22 can further include a diesel particulate filter (DPF) 38, a diesel oxidation catalyst (DOC) 42, and an ammonia oxidation (AMOx) catalyst 54. The SCR system 46 further includes a reductant delivery mechanism that has a diesel exhaust fluid (DEF) source 58 that supplies DEF to a DEF dosing mechanism 62 via a DEF line 64.

[0039] In an exhaust flow direction, as indicated by directional arrow 66, exhaust gas flows from the engine 18 into an exhaust manifold 68, and into inlet piping 70 of the exhaust aftertreatment system 22. In embodiments that include the DPF 38 and the DOC 42, from the inlet piping 70, the exhaust gas flows into the DOC 42 and exits the DOC 42 into a first section of exhaust piping 74A. From the first section of exhaust piping 74A, the exhaust gas flows into the DPF 38 and exits the DPF 38 into a second section of exhaust piping 74B. From the second section of exhaust piping 74B, the exhaust gas flows into the SCR catalyst 50 and exits the SCR catalyst 50 into the third section of exhaust piping 74C. As the exhaust gas flows through the second section of exhaust piping 74B, it is periodically dosed with DEF by the DEF dosing mechanism 62. Accordingly, the second section of exhaust piping 74B acts as a decomposition chamber or tube to facilitate the decomposition of the DEF to ammonia. In embodiments that include the AMOx catalyst 54, from the third section of exhaust piping 74C, the exhaust gas flows into the AMOx catalyst 54 and exits the AMOx catalyst 54 into the outlet piping 78 before the exhaust gas is expelled from the exhaust aftertreatment system 22. In embodiments that do not include the DPF 38 and the DOC 42, the exhaust gas flows from the 68 68 to the SCR catalyst 50. Based on the foregoing, in the illustrated embodiment, the SCR catalyst 50 is positioned upstream of the AMOx catalyst 54. However, in alternative embodiments, other arrangements of the components of the exhaust aftertreatment system 22 are also possible (e.g., the AMOx catalyst 54 may be excluded from the exhaust aftertreatment system 22).

[0040] As discussed above and in this example configuration, the SCR system 46 includes a reductant delivery mechanism with a reductant (e.g., DEF) source, pump (not shown) and delivery mechanism or dosing mechanism 62. The reductant source can be a container or tank capable of retaining a reductant, such as, for example, ammonia (NH3), DEF (e.g., urea), or diesel oil. The reductant source is in reductant supplying communication with the pump, which is configured to pump reductant from the reductant source to the delivery mechanism 62 via a reductant delivery line. The delivery mechanism 62 is positioned upstream of the SCR catalyst 50. The delivery mechanism 62 is selectively controllable (e.g., by the controller 26) to inject reductant directly into the exhaust gas prior to entering the SCR catalyst 50. As described herein, the controller 26 is structured to control the timing and amount of the reductant delivered to the exhaust gas. In some embodiments, the reductant may either be ammonia or DEF, which decomposes to produce ammonia. As briefly described above, the ammonia reacts with NOx in the presence of the SCR catalyst 50 to reduce the NOx to less harmful emissions, such as N2 and H2O. The NOx in the exhaust gas includes NO2 and NO. Generally, both NO2 and NO are reduced to N2 and H2O through various chemical reactions driven by the catalytic elements of the SCR catalyst 50 in the presence of NH3.

[0041] The SCR catalyst 50 may be any of various catalysts known in the art. For example, in some embodiments, the SCR catalyst 50 is a vanadium-based catalyst, and in other embodiments, the SCR catalyst 50 is a zeolite-based catalyst, such as a Cu-Zeolite or a FeZeolite catalyst. In one representative embodiment, the reductant is aqueous urea and the SCR catalyst 50 is a vanadium-based catalyst.

[0042] In some embodiments, an efficiency of the SCR catalyst 50 is temperature dependent, meaning that the SCR catalyst 50 is more efficient at reducing the NOx into less-harmful emissions at various temperature ranges compared to other temperature ranges. For example, in some embodiments, the SCR catalyst 50 is more efficient at reducing NOx into less-harmful emissions at higher temperatures.

[0043] An effectiveness of the SCR catalyst 50 is based on a space velocity of the exhaust gas through the SCR system 46 and the temperature of the SCR catalyst 50. The phrase "space velocity" is generally used herein to refer to a volumetric flow rate exhaust gas through the SCR catalyst 50 normalized with respect to a volume of the SCR catalyst 50. Accordingly, an increase in the space velocity is indicative of an increase in the exhaust flow. The space velocity provides a measure of an amount of time that the exhaust gas is exposed to the SCR catalyst 50 and can react with the SCR catalyst 50. Since the SCR catalyst 50 operates more efficiently at higher temperatures, the SCR catalyst 50 can effectively convert the NOx in exhaust gas having high space velocities. In contrast, since the SCR catalyst 50 operates less efficiently at lower temperatures, the SCR catalyst 50 cannot effectively convert the NOx in exhaust gas having a high space velocity. Accordingly, the engine out NOx is reduced for operating conditions in which the SCR catalyst 50 has a relatively low temperature and the exhaust gas a high space velocity. In some embodiments, the relatively low temperature can include temperatures at or below 250°C.

[0044] The AMOx catalyst 54 may be any of various flow-through catalysts configured to react with ammonia to produce mainly nitrogen. As briefly described above, the AMOx catalyst 54 is structured to remove ammonia that has slipped through or exited the SCR catalyst 50 without reacting with NOx in the exhaust gas. In certain instances, the exhaust aftertreatment system 22 can be operable with or without the AMOx catalyst 54. Further, although the AMOx catalyst 54 is shown as a separate unit from the SCR catalyst 50 in FIG. I, in some embodiments, the AMOx catalyst 54 may be integrated with the SCR catalyst 50, e.g., the AMOx catalyst 54 and the SCR catalyst 50 can be located within the same housing.

[0045] Various sensors, such as NOx sensors and temperature sensors, may be strategically disposed throughout the exhaust aftertreatment system 22 and may be in communication with the controller 26 to monitor operating conditions of the engine system 14. In this regard, the controller 26 may receive data from the one or more sensors. As shown in FIG. 1, the exhaust aftertreatment system 22 includes a temperature sensor 86, a temperature sensor 88, a NOx sensor 90, a NOx sensor 92, an air intake sensor 94, and an exhaust sensor 96. The temperature sensor 88 is positioned between an exhaust outlet of the engine and an inlet of the SCR system 46 for determining the temperature of the exhaust gas as or before the exhaust gas enters the SCR system 46. The temperature sensor 92 is positioned proximate and/or at an outlet of the SCR system 46 for determining the temperature of the exhaust gas leaving the SCR system 46. The NOx sensor 92 is positioned proximate and/or at the inlet of the SCR system 46 for determining a NOx concentration of the exhaust gas entering the SCR system 46. The NOx sensor 92 is positioned at and/or proximate an outlet of the SCR system 46 to determine a NOx concentration of the exhaust gas leaving the SCR system 46. The air intake sensor 94 is positioned proximate and/or at an inlet of an air intake inlet (e.g., of the intake manifold or a turbocharger inlet) of the engine 18 for determining a flow rate of the air entering the engine 18. The exhaust sensor 96 is positioned between the exhaust outlet of the engine 18 and the inlet of the SCR system 46 for determining the temperature of the exhaust gas as or before the exhaust gas enters the SCR system 46.

[0046] Although the exhaust aftertreatment system 22 shown includes one of the SCR catalyst 50 and AMOx catalyst 54 positioned in specific locations relative to each other along the exhaust flow path, in other embodiments, the exhaust aftertreatment system 22 may include more than one of any of the various catalysts positioned in any of various positions relative to each other along the exhaust flow path as desired. Further, although the DOC 42 and AMOx catalyst 54 are non-selective catalysts, in some embodiments, the DOC 42 and AMOx catalyst 54 can be selective catalysts.

[0047] The DOC 42 may have any of various flow-through designs. Generally, the DOC 42 is structured to oxidize at least some particulate matter, e.g., the soluble organic fraction of soot, in the exhaust gas and reduce unburned hydrocarbons and CO in the exhaust gas to less environmentally harmful compounds. For example, the DOC 42 may be structured to reduce the hydrocarbon and CO concentrations in the exhaust to meet the requisite emissions standards for those components of the exhaust gas. An indirect consequence of the oxidation capabilities of the DOC 42 is the ability of the DOC 42 to oxidize NO into NO2. In this manner, the level of NO, exiting the DOC 42 is equal to the NO2 in the exhaust gas generated by the engine 18 plus the NO2 converted from NO by the DOC 42.

[0048] The DPF 38 may be any of various flow-through designs, and is structured to reduce particulate matter concentrations, e.g., soot and ash, in the exhaust gas to meet one or more requisite emission standards. The DPF 38 captures particulate matter and other constituents, and thus needs to be periodically regenerated to burn off the captured constituents. Additionally, the DPF 38 may be configured to oxidize NO to form NO2 independent of the DOC 42.

[0049] Based on the foregoing, in the illustrated embodiment, the DOC 42 is positioned upstream of the DPF 38 and the SCR catalyst 50, and the SCR catalyst 50 is positioned downstream of the DPF 38 and upstream of the AMOx catalyst 54. However, in alternative embodiments, other arrangements of the components of the exhaust aftertreatment system 22 are also possible (e.g., the AMOx catalyst 54 may be excluded from the exhaust aftertreatment system 22). For example, in some embodiments, the exhaust aftertreatment system 22 can include one of the DOC 42 and the DPF 38. In other embodiments, the exhaust aftertreatment system 22 can include neither the DOC 42 nor the DPF 38. In such embodiments, the vehicle components are positioned in conjunction with the principles described above.

[0050] FIG. 1 is also shown to include the operator I/O device 30. The operator I/O device 30 is communicably coupled to the controller 26, such that information may be exchanged between the controller 26 and the operator I/O device 30, wherein the information may relate to one or more components of FIG. 1 or determinations/commands/instructions/etc. (described below) of the controller 26. The operator I/O device 30 enables an operator of the vehicle (or another passenger) to communicate with the controller 26 and one more components of the vehicle and components of FIG. 1. For example, the operator I/O device 30 may include, but is not limited to, an interactive display, a touchscreen device, one or more buttons and switches, voice command receivers, etc. Via the operator I/O device 30, the controller 26 may provide various information concerning the operations described herein.

[0051] The controller 26 is structured to control, at least partly, the operation of the engine system 14 and associated sub-systems, such as the internal combustion engine 18 and the exhaust aftertreatment system 22. According to one embodiment, the components of FIGS. 1 -2 are embodied in the vehicle 10. The vehicle 10 may include an on-road or an off-road vehicle including, but not limited to, line-haul trucks, mid-range trucks (e.g., pick-up trucks), tanks, airplanes, and any other type of vehicle that utilizes an SCR system. Communication between and among the components may be via any number of wired or wireless connections. For example, a wired connection may include a serial cable, a fiber optic cable, a CATS cable, or any other form of wired connection. In comparison, a wireless connection may include the Internet, Wi-Fi, cellular, radio, etc. In one embodiment, a controller area network (CAN) bus provides the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections. Because the controller 26 is communicably coupled to the systems and components of FIG. 1, the controller 26 is structured to receive data from one or more of the components shown in FIG. 1. For example, the data may include temperature data, (e.g., a temperature of the exhaust gas at or before the inlet of the SCR system 46, a temperature of the exhaust gas at or before the outlet of the SCR system 46), NOx data (e.g., an incoming NOx amount from NOx sensor 92 and an outgoing NOx amount from NOx sensor 92), air intake velocity data (e.g., a flow rate of air into the engine from airflow sensor 94 positioned proximate an air intake of the engine 18 or an air intake of a turbo charge system), exhaust gas velocity data (e.g., a flow rate of the exhaust gas proximate an outlet of the engine, a flow rate of the exhaust gas proximate an inlet of the SCR system 46, or a flow rate of the exhaust gas existing the SCR system 46), and a vehicle operating data (e.g., engine speed, engine temperature, exhaust gas temperature, etc.) received via one or more sensors. As another example, the data may include an input from operator I/O device 30. The structure and function of the controller 26 is further described in regard to FIG. 2.

[0052] Referring now to FIG. 2, a schematic diagram of the controller 26 of the vehicle of FIG. 1 is shown according to an example embodiment. As shown in FIG. 2, the controller 26 includes a processing circuit 102 having a processor 106 and a memory device 110, a SCR storage circuit 114, a SCR space velocity circuit 118, and an engine operation circuit 126. Generally, the controller 26 is structured to determine a) a temperature status of the SCR catalyst 50 and b) an ammonia storage status of the SCR catalyst 50. The controller 26 then determines engine operating parameters based on the temperature status of the SCR catalyst 50 and the ammonia storage status of the SCR catalyst 50. The engine operating parameters can include fuel injection timing, fuel pressure, charge flow through a turbo charger, and/or a position of an exhaust gas recirculation (EGR) valve.

[0053] In one configuration, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 are embodied as machine or computer-readable media that is executable by a processor, such as the processor 106. As described herein and amongst other uses, the machine-readable media facilitates performance of certain operations to enable reception and transmission of data. For example, the machine-readable media may provide an instruction (e.g., command, etc.) to, e.g., acquire data from a particular physical sensor or a particular virtual sensor. In this regard, the machine-readable media may include programmable logic that defines the frequency of acquisition of the data (or, transmission of the data). The computer readable media may include code, which may be written in any programming language including, but not limited to, Java or the like and any conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program code may be executed on one processor or multiple remote processors. In the latter scenario, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

[0054] In another configuration, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 are embodied as hardware units, such as electronic control units. As such, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may be embodied as one or more circuitry components including, but not limited to, processing circuitry, network interfaces, peripheral devices, input devices, output devices, sensors, etc. In some embodiments, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may take the form of one or more analog circuits, electronic circuits (e.g., integrated circuits (IC), discrete circuits, system on a chip (SOCs) circuits, microcontrollers, etc.), telecommunication circuits, hybrid circuits, and any other type of "circuit." In this regard, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may include any type of component for accomplishing or facilitating achievement of the operations described herein. For example, a circuit as described herein may include one or more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, and so on). The SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may also include programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. The SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may include one or more memory devices for storing instructions that are executable by the processor(s) of the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126. The one or more memory devices and processor(s) may have the same definition as provided herein with respect to the memory device 110 and the processor 106. In some hardware unit configurations, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may be geographically dispersed throughout separate locations in the vehicle. Alternatively and as shown, the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may be embodied in or within a single unit/housing, which is shown as the controller 26.

[0055] In the example shown, the controller 26 includes a processing circuit 102 having the processor 106 and the memory device 110. The processing circuit 102 may be structured or configured to execute or implement the instructions, commands, and/or control processes described herein with respect to the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126. Thus, the depicted configuration represents the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 as machine or computer-readable media. However, as mentioned above, this illustration is not meant to be limiting as the present disclosure contemplates other embodiments where the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 or the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 is configured as hardware units. All such combinations and variations are intended to fall within the scope of the present disclosure.

[0056] The processor 106 may be implemented as one or more general-purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a digital signal processor (DSP), a group of processing components, or other suitable electronic processing components. In some embodiments, the one or more processors may be shared by multiple circuits (e.g., the SCR storage circuit 114, the SCR space velocity circuit 118, and the engine operation circuit 126 may comprise or otherwise share the same processor which, in some example embodiments, may execute instructions stored, or otherwise accessed, via different areas of memory). Alternatively or additionally, the one or more processors may be structured to perform or otherwise execute certain operations independent of one or more co-processors. In other example embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multi-threaded instruction execution. All such variations are intended to fall within the scope of the present disclosure. The memory device 110 (e.g., RAM, RONI, Flash Memory, hard disk storage, etc.) may store data and/or computer code for facilitating the various processes described herein. The memory device 110 may be communicably connected to the processor 106 to provide computer code or instructions to the processor 106 for executing at least some of the processes described herein. Moreover, the memory device 110 may be or include tangible, non-transient volatile memory or non-volatile memory. Accordingly, the memory device 110 may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

[0057] The memory device 110 includes low NOx combustion parameters130, high NOx combustion parameters134, SCR catalyst storage parameters 138, and space velocity parameters 142. The low NOx combustion parameters 130 are engine operating parameters that are configured to generate exhaust gas having a relatively low NOx concentration. The high NOx combustion parameters 134 are engine operating parameters that are configured to generate exhaust having a relatively high NOx concentration. The low NOx combustion parameters 130 include at least a fuel injection timing lookup table and a fuel pressure lookup table. The low NOx combustion parameters 130 can include an auxiliary fuel injection table that includes fuel injection timing data and amount of fuel dispensed data. In embodiments in which the engine 18 includes a turbocharger (not shown), the low NOx combustion parameters 130 further include a charge flow lookup table 154. In embodiments in which the engine 18 includes an exhaust gas recirculation (EGR) valve, the low NOx combustion parameters 130 further include an EGR valve position look-up table. The high NOx combustion parameters 134 include at least a fuel injection timing lookup table and a fuel pressure lookup table. The low NOx combustion parameters 130 can include an auxiliary fuel injection table that includes fuel injection timing data and amount of fuel dispensed data. In embodiments in which the engine 18 includes the turbocharger, the high NOx combustion parameters 134 further include a charge flow lookup table. In embodiments in which the engine 18 includes an exhaust gas recirculation (EGR) valve, the high NOx combustion parameters 134 further include an EGR valve position lookup table.

[0058] The SCR catalyst storage parameters 138 are used to determine a target ammonia storage state of the SCR catalyst 50. In some embodiments, the target ammonia storage state can be based on an amount of ammonia bound to the SCR catalyst 50. In some embodiments, the target ammonia storage state can be a storage capacity that is based on an amount of NOx that the ammonia bound to the SCR catalyst 50 can absorb. In some embodiments, the target ammonia storage state can be based on the temperature of the SCR catalyst 50. For example, in some embodiments, the SCR catalyst storage parameters H8 can include a lookup table that includes target ammonia storage state values based on the temperature of the SCR catalyst. For example, the target ammonia storage state can be 1 g ammonia per 1 liter of exhaust at a SCR catalyst 50 temperature of approximately 220 °C. The target ammonia storage state can be no stored ammonia at a SCR catalyst 50 temperature of approximately 400 °C.

[0059] The space velocity parameters 142 are used to determine a critical space velocity (e.g., a space velocity threshold) of exhaust flow through the SCR catalyst 50. The critical space velocity is based on a temperature of the SCR catalyst 50 is indicative of a maximum exhaust gas flow rate through the SCR catalyst 50 that can yield sufficient removal of NOx from the exhaust gas. In the illustrated embodiment, the space velocity parameters 142 include a lookup table in which the critical space velocity can be determined based on the temperature of the exhaust gas at or proximate the inlet of the SCR system 46 and the temperature of the exhaust gas at or proximate the outlet of the SCR system 46.

[0060] The communications interface 172 may be/include any combination of wired or wireless interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) for conducting data communications with various systems, devices, or networks. For example, the communications interface 172 may include an Ethernet card and port for sending and receiving data via an Ethernet-based communications network and/or a Wi-Fi transceiver for communicating via a wireless communications network. The communications interface 172 may be structured to communicate via local area networks or wide area networks (e.g., the Internet, etc.) and may use a variety of communications protocols (e.g., IP, LON, Bluetooth, ZigBee, radio, cellular, near field communication, etc.).

[0061] The communications interface 172 of the controller 26 may facilitate communication between and among the controller 26 and one or more components of the vehicle (e.g., components of vehicle subsystems (such as the engine system 14, the exhaust aftertreatment system 22), the operator I/O device 30, the sensors, etc.). Communication between and among the controller 26 and the components of the vehicle may be via any number of wired or wireless connections (e.g., any standard under IEEE 802, etc.). For example, a wired connection may include a serial cable, a fiber optic cable, a CATS cable, or any other form of wired connection. In comparison, a wireless connection may include the Internet, Wi-Fi, cellular, Bluetooth, ZigBee, radio, etc. In one embodiment, a controller area network (CAN) bus provides the exchange of signals, information, and/or data. The CAN bus can include any number of wired and wireless connections that provide the exchange of signals, information, and/or data. The CAN bus may include a local area network (LAN), or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0062] The SCR storage circuit 114 is structured to receive information indicative of a storage state of the SCR catalyst 50 of the exhaust aftertreatment system 22. The SCR storage circuit 114 is structured to determine a storage state of the SCR catalyst 50 based on the information indicative of the ammonia storage state. For example, the information indicative of the storage state of the SCR catalyst 50 can be the SCR catalyst 50 temperature, a urea dosing to NOx ratio, and/or an ammonia dosing to NOx ratio. The information indicative of the storage state of the SCR catalyst 50 can be previously determined for the vehicle 10 or can be based on experimentally-determined data. The SCR storage circuit 114 is structured to determine the storage state of the SCR catalyst 50 based on a predictive model and/or a look up table. The SCR storage circuit 114 is further structured to determine the target ammonia storage state of the SCR catalyst 50 based on the SCR catalyst storage parameters 138 stored in the memory device 110.

[0063] The SCR storage circuit 114 is structured to receive the determined ammonia storage state of the SCR catalyst 50. The SCR storage circuit 114 is structured to compare the determined ammonia storage state of the SCR catalyst 50 to the target ammonia storage state of the SCR catalyst 50. For example, the SCR storage circuit 114 can be structured to determine a difference between the determined ammonia storage state of the SCR catalyst 50 and the target ammonia storage state of the SCR catalyst 50. The SCR storage circuit 114 can then compare the determined difference to a difference threshold. The difference threshold is a parameter indicates a maximum difference between the determined ammonia storage capacity of the SCR storage catalyst 50 and the target ammonia storage capacity of the SCR storage catalyst. In response to the difference being above the difference threshold, the SCR storage circuit 114 can set the SCR storage state variable 178 to a low NOx state indicating that the low NOx combustion parameters 130 should be used. In response to the difference being at or below the difference threshold, the SCR storage circuit 114 can set the SCR storage state variable 178 to a high NOx state or second state indicating that the high NOx combustion parameters 134 can be used.

[0064] The SCR space velocity circuit 118 is structured to receive information indicative of an exhaust gas flow rate through the SCR catalyst 50 and information indicative of a temperature of the SCR catalyst 50. The information indicative of the exhaust gas flow rate through the SCR catalyst 50 can include an exhaust gas flow rate leaving the engine 18 determined by a sensor positioned proximate an outlet of the engine 18, a flow rate of exhaust entering the SCR system 46 determined by a sensor positioned proximate an inlet of the SCR system 46, and/or a flow rate of exhaust gas leaving the SCR system 46 determined by a sensor positioned proximate an outlet of the SCR system 46. The information indicative of the temperature of the SCR catalyst 50 can be a temperature of the exhaust gas proximate an inlet of the SCR catalyst 50 and a temperature of the exhaust gas proximate an outlet of the SCR catalyst 50. The SCR space velocity circuit 118 is structured to determine a space velocity of the exhaust gas based on the information indicative of the exhaust gas flow rate through the SCR catalyst 50 and a volume of the SCR catalyst 50. For example, the SCR space velocity circuit may determine a volumetric flow rate of the exhaust gas based on the information indicative of the exhaust gas flow rate and divide the determined volumetric flow rate of the exhaust gas by the volume of the SCR catalyst 50. The SCR space velocity circuit 118 is structured to access the space velocity parameters 142 to determine the critical velocity of the exhaust gas based on the information indicative of the temperature of the SCR catalyst 50.

[0065] In some embodiments, the SCR space velocity circuit 118 is structured to receive information indicative of an amount of air entering the engine 18. The information indicative of an amount of air entering the engine 18 may be a flow rate of air entering the engine 18 through the engine intake manifold and/or the information indicative of air entering the engine 18 may be a flow rate of air entering the engine 18 through the turbocharger. The SCR space velocity circuit 118 can predict a future space velocity of exhaust gas through the SCR catalyst 50 based on the information indicative of the amount of air entering the engine 18 either alone or in conjunction with other operating parameters of the engine 18. The engine operation circuit 126 can control the engine combustion parameters based on the predicted future space velocity of exhaust gas through the SCR catalyst 50 in a manner similar to what is described below with respect to the determined space velocity.

[0066] The SCR space velocity circuit 118 is further structured to compare the determined space velocity of the exhaust gas to the critical velocity. In response to determining that the determined space velocity is greater than or equal to the critical velocity, the SCR space velocity circuit 118 can set a space velocity state variable 182 to a low NOx or first state indicating that the low NOx combustion parameters 130 should be used. In response to determining that the determined space velocity is less than the critical space velocity, the SCR space velocity circuit 118 can set the space velocity state variable 182 to a high NOx or second state indicating that the high NOx combustion parameters 134 can be used.

[0067] The engine operation circuit 126 is further structured to determine the engine combustion parameters based on the state of the SCR storage state variable 178 and the state of the space velocity state variable 182. In some embodiments, the ermine operation circuit 126 may determine the engine combustion parameters using a logical AND gate. In response to determining that at least one of the SCR storage state variable 178 is in the low NOx state (e.g., the difference between the determined state of the SCR catalyst 50 and the target ammonia storage state of the SCR catalyst 50 is above the difference threshold) and the space velocity state variable 182 is in the low NOx state, the engine operation circuit 126 is structured to determine that the engine 18 should be operated according to the low NOx combustion parameters 130. In response to determining that the SCR storage state variable 178 is in the high NOx state (e.g., the difference between the determined state of the SCR catalyst 50 and the target ammonia storage state of the SCR catalyst 50 is below the difference threshold) and the space velocity state variable 182 is in the high NOx state, the engine operation circuit 126 is structured to operate the engine 18 according to the high NOx combustion parameters 134.

[0068] The engine operation circuit 126 is in communication with the SCR storage circuit 114 and the engine 18. The engine operation circuit 126 is structured to retrieve information indicative of the engine combustion parameters from the SCR storage circuit 114. In response to receiving information indicating that the engine 18 should operate according to the low NOx combustion parameters 130, the engine operation circuit 126 is structured to retrieve the low NOx combustion parameters 130 from the memory device 110 and operate the engine according to the low NOx combustion parameters. In response to receiving information indicating that the engine 18 can operate according to the high NOx combustion parameters 134, the engine operation circuit 126 is structured to retrieve the high NOx combustion parameters 134 from the memory device 110 and operate the engine 18 according to the high NOx combustion parameters 134.

[0069] Operation of the engine 18 in the high NOx mode improves the BSFC of the engine 18. Accordingly, the engine 18 can generate more power for the amount of fuel consumed when operating according to the high NOx combustion parameters 134 than when the engine 18 is operating according to the low NOx combustion parameters 130. In some embodiments, the engine operation circuit 126 can include an increased power mode and a reduced fuel consumption mode. The increased power mode is structured to generate more power when the engine 18 is operating according to the high NOx combustion parameters 134 relative to when the engine 18 is operating according to the low NOx combustion parameters 130. For example, in the increased power mode, the fuel injection parameters of the high NOx combustion parameters 134 can be substantially the same as fuel injection parameters of the low NOx combustion parameters 130. As used herein, the phrase "fuel injection parameters" generally refers to fueling quantity per stroke and/or overall fuel injection rate. Since the engine 18 operates with a lower BSFC under the high NOx combustion parameters 134 while consuming substantially a same amount of fuel as the engine operating under the low NOx combustion parameters 130, the engine 18 generates more power when operating according to the high NOx combustion parameters 134.

[0070] The reduced fuel consumption mode is structured to consume less fuel when the engine 18 is operated according to the high NOx combustion parameters 134 relative to when the engine 18 is operated according to the low NOx combustion parameters 130. For example, in the reduced fuel consumption mode, the fuel injection parameters of the high NOx combustion parameters 134 can be lower than fuel injection parameters of the low NOx combustion parameters 130. Since the engine 18 operates with a higher BSFC under the high NOx combustion parameters 134, the engine 18 operating according to the high NOx combustion parameters 134 can consume less fuel to generate substantially a same amount of power as the engine 18 operated according to the low NOx combustion parameters 130.

[0071] In some embodiments, the mode of the engine operation circuit 126 can be set by an operator of the system (e.g., using the operator I/O device 30) and/or set automatically based on driving conditions. In such embodiments, the memory device 110 may include high NOx combustion parameters and low NOx combustion parameters for the increased power mode and high NOx combustion parameters and low NOx combustion parameters for the reduced fuel consumption mode. In other embodiments, the engine operation circuit 126 may only include the increased power mode or the reduced fuel consumption mode.

[0072] FIG. 3 illustrates a method 186 for operating the engine 18 based on the conditions of the SCR catalyst 50 according to an example embodiment. The engine 18 may be generating a driving force for propelling the vehicle 10. At process 190, the SCR storage circuit 114 receives information indicative of the storage state of the SCR catalyst 50. At process 194, the SCR storage circuit 114 determines the storage state of the SCR catalyst 50 based on the information indicative of the storage state of the SCR catalyst 50. For example, in some embodiments, the information indicative of the storage state of the SCR catalyst 50 can be based on a model, information contained in a lookup table, etc. [0073] At process 198, the SCR space velocity circuit 118 receives information indicative of an exhaust gas flow rate through the SCR catalyst 50. The information indicative of the exhaust gas flow rate through the SCR catalyst 50 may be a volumetric flow rate. At process 202, the SCR space velocity circuit 118 determines the space velocity of the exhaust gas through the SCR catalyst 50. For example, the SCR space velocity circuit 118 may divide the information indicative of the exhaust gas flow rate through the SCR catalyst 50 by a volume of the SCR catalyst 50. At process 206, the SCR space velocity circuit 118 receives information indicative of a temperature of the SCR catalyst 50. For example, the SCR space velocity circuit 118 may receive a temperature of the exhaust gas entering the SCR system 46 determined by a sensor positioned proximate an inlet of the SCR system 46 and a temperature of the exhaust gas leaving the SCR system 46 determined by a sensor positioned proximate an outlet of the SCR system 46. At process 210, the SCR space velocity circuit determines the critical space velocity of the exhaust gas in the SCR system 46. For example, the SCR space velocity circuit 118 may access the space velocity parameters 142 stored in the memory device 110 to determine the critical velocity of the exhaust gas based on the information indicative of the temperature of the SCR catalyst 50.

[0074] At process 218, the SCR storage circuit 114 compares the determined ammonia storage state of the SCR catalyst 50 to a target state of the SCR catalyst 50. The SCR storage circuit 114 may determine the target state of the SCR catalyst 50 from the SCR catalyst storage parameters 138 stored in the memory device 110. At process 222, the SCR storage circuit 114 sets the SCR storage state variable 178 to the high NOx state or the low NOx state based on the comparison. In some embodiments, the SCR storage circuit 114 may determine a difference between the determined SCR storage state and the target SCR storage state and compare the determined difference to a difference threshold. In response to the comparison indicating the determined difference is larger than the difference threshold, the SCR storage circuit 114 is structured to set the SCR storage state variable 178 to the low NOx state, indicating that the low NOx combustion parameters should be used. In response to the comparison indicating the determined difference is less than the difference threshold, the SCR storage circuit 114 is structured to set the SCR storage state variable 178 to the high NOx state, indicating that the high NOx combustion parameters can be used.

[0075] At process 230, the SCR space velocity circuit 118 is further structured to compare the determined space velocity of the exhaust gas to the critical space velocity. In response to determining that the determined space velocity is greater than or equal to the critical space velocity, the SCR space velocity circuit 118 can set the space velocity state variable 182 to the low NOx state, indicating that the low NOx combustion parameters 130 should be used. In response to determining that the determined space velocity is less than the critical velocity, the SCR space velocity circuit 118 can set the critical space velocity state variable 182 to the high NOx state, indicating that the high NOx combustion parameters 134 should be used.

[0076] At process 234, the engine operation circuit 126 determines the engine combustion parameters based on the state of the SCR storage state variable 178 and the state of the space velocity state variable 182. For example, in response to determining that at least one of the SCR storage state variable and the space velocity variable is in the low NOx state, the engine operation circuit 126 determines that the engine 18 should operate according to the low NOx combustion parameters 130. In response to determining that the SCR storage state variable 178 and the space velocity state variable 182 are in the high NOx state, the engine operation circuit 126 determines that the engine 18 can operate according to the high NOx combustion parameters 134. At process 246, the engine operation circuit 126 operates the engine 18 according to the low NOx combustion parameters 130 or the high NOx combustion parameters 134.

[0077] The method 186 then returns to process 190. Accordingly, the method 186 can switch between operating the engine 18 according to the low NOx combustion parameters 130 and the high NOx combustion parameters 134 based on the operating conditions of the SCR system 46. In some embodiments, the method 186 can facilitate switching between the low NOx combustion parameters 130 and the high NOx combustion parameters 134 in real time or in substantially real time. Accordingly, the method 186 can maximize an amount of time that the engine 18 spends operating according to the more efficient high NOx combustion parameters 134 while maintaining acceptable vehicle (e.g., tailpipe) NOx emissions by commanding the engine 18 to operate according to the low NOx combustion parameters 130 based on the operating conditions of the SCR system 46.

[0078] FIGS. 4 -6 illustrate graphs comparing engine operating conditions of a conventional engine and the engine 18 operating according to the method 186. FIG. 4 illustrates a boxplot of an amount of NOx in the exhaust gas leaving the engine outlet for both the conventional engine and the engine 18. The engine outlet NOx of the conventional engine is approximately 7.23 g/kWh. The engine outlet NOx of the engine 18 is approximately 8.01 g/kWh. Accordingly, operating the engine 18 according to the method 186 can generate exhaust gas having approximately 10% more NOx than the conventional engine. This indicates that the engine 18 is spending approximately 10% more time operating under the more efficient high NOx combustion parameters 134.

[0079] FIG. 5 illustrates a boxplot of an amount of NOx in the exhaust gas (e.g., tailpipe exhaust gas) leaving a conventional vehicle including the conventional engine and the vehicle 10 including the engine 18 that is operated according to the method 186. The vehicle outlet NOx for the conventional vehicle is approximately 0.194 g/kWh. The vehicle outlet NOx of the vehicle 1 0 is approximately 0.206 g/kWh. A p-value for equal variance between the conventional system out NOx and the system out NOx of the engine operating according to the method 186 is 0.737. Accordingly, a difference between the system outlet NOx of the conventional engine and the engine 18 is not statistically significant, despite the fact that the engine 18 generated exhaust gas having approximately 10% more NOx than the conventional engine. This result indicates that the exhaust aftertreatment system 22 (e.g., the SCR catalyst 50) is able to spend more time operating under the high NOx operating conditions relative to a conventional vehicle while having substantially the same NOx as the exhaust gas leaving the conventional vehicle. Accordingly, the method 186 causes the engine 18 to operate according to the higher efficiency high NOx combustion parameters 134 without resulting in higher NOx exhaust gas (e.g., tailpipe) emissions in the vehicle 10.

[0080] FIG. 6 illustrates a boxplot of a BSFC for the conventional engine and the engine 18 operating according to the method 186. The BSFC of the conventional engine is approximately 234.3 g/kWh. The BSFC of the engine 18 is approximately 231.6 g/kWh. Accordingly, the method 186 improves the BSFC of the engine 18 by 1.1% relative to the conventional engine. A p-value for equal variance between the BSFC of the conventional engine and the BSFC of the engine operating according to the method 186 is 0.011. Accordingly, the 1.1% difference in BSFC is statistically significant. Therefore, the method 186 can improve the BFSC of the engine IS such that the engine 18 is producing I l% more power than the conventional engine or using 1.1% less fuel than the conventional engine while generating substantially the same vehicle NOx emissions.

[0081] FIGS. 7 and 8 illustrate emissions test results for an engine operating under first conditions 250 and the engine operating under second conditions 254. In the illustrated embodiment, the engine operating under the first conditions 250 has been operated at maximum power for approximately twenty minutes before testing. The engine operating under the second conditions 254 has been operated according the testing cycle for three previous cycles. FIG. 7 illustrates a cumulative vehicle exhaust (e.g., tailpipe exhaust) output NOx plot 258 for the first conditions 250 and the second conditions 254, a space velocity plot 262 of the exhaust gas through the SCR catalyst 50 for the first conditions 250 and the second conditions 254, and a SCR catalyst 50 temperature plot 266 for the first conditions 250 and the second conditions 254. More specifically, the plot 266 illustrates an average of a SCR inlet temperature and an SCR outlet temperature. FIG. 8 illustrates a plot 270 of the ratio of the actual ammonia storage capacity of the SCR catalyst 50 at a given temperature for the first conditions 250 and the second conditions 254. FIG. 8 also illustrates a plot 274 of the ratio between the target ammonia storage state of the SCR catalyst 50 and the storage capacity of the SCR catalyst 50 at the given temperature.

[0082] Referring now to FIG. 7, and more specifically to the cumulative vehicle exhaust outlet NOx plot 258, the cumulative vehicle exhaust outlet NOx plot 258 includes substantially flat (e.g., horizontal) portions and increasing portions. The substantially flat portions indicate that the SCR catalyst 50 is effectively removing the NOx from the exhaust gas. The SCR catalyst 50 may be able to remove more NOx if it were present at the substantially flat portions (e.g., if the engine were operated according to higher NOx combustion parameters in the conditions that yield the substantially flat portions). The increasing portions indicate a presence of unconverted NOx in the system out NOx stream. As shown in FIG. 7, when operating under the first conditions 250, the cumulative vehicle exhaust outlet NOx plot includes a first flat portion 278, a second flat portion 282, a first increasing portion 286, a second increasing portion 290, a third increasing portion 294, and a fourth increasing portion 298. When operating under the second conditions 254, the cumulative vehicle exhaust outlet NOx plot includes a first flat portion 302, a second flat portion 306, a third flat portion 310, a first increasing portion 314, a second increasing portion 318, and a third increasing portion 322. As illustrated in FIG. 7, the first increasing portion 286 under the first conditions 250 and the first increasing portion 314 under the second conditions 254 occur at substantially a same time, the third increasing portion 294 under the first conditions 250 and the second increasing portion 318 under the second conditions 254 occur at substantially a same time, and the fourth increasing portion 298 under the first conditions 250 and the third increasing portion 322 under the second conditions 254 occur at substantially a same time. The increasing portions 286, 294, 298 under the first conditions 250 and the increasing portions 314, 318, 322 under the second conditions 254 occur during spikes in the space velocity.

[0083] The first flat portion 278 under the first conditions 250 and the second flat portion 306 under the second conditions 254 occur at substantially a same time and occur during a relatively low space velocity. The second flat portion 282 under the first conditions 250 and the third flat portion 310 under the second conditions 254 occur at substantially a same time and at a space velocity that is initially relatively high and then decreases. The second increasing portion 290 under the first conditions 250 and the first flat portion 302 under the second conditions 254 occur substantially a same time and for a relatively low space velocity. A temperature of the SCR catalyst under the first conditions 250 is higher than the SCR temperature of the SCR catalyst under the second conditions 254 during the second increasing portion 290 and the first flat portion 302. As shown in the plot 266, the SCR catalyst temperature under the first operating conditions 250 is generally higher than the SCR catalyst temperature the second operating conditions 254 until approximately 700 seconds into the testing period because the engine operated at maximum power (and therefore higher temperatures) for approximately 20 minutes before the start of the first test conditions 250. As can be seen by comparing plots 258 and 266, the first operating conditions 250 have a higher temperature than the second operating conditions 254 during the time period ranging between 0 seconds and approximately 700 seconds, which is the time period in which the rate of cumulative vehicle outlet exhaust NOx generated under the first conditions 250 increases the most relative to the cumulative vehicle outlet exhaust NOx generated under the second conditions 254. Accordingly, based on the plots 258, 262, 266, the space velocity of the exhaust gas through the SCR catalyst 50 and the temperature of the SCR catalyst 50 both appear to impact an amount of NOx in the vehicle outlet exhaust gas.

[0084] FIG. 8 illustrates the plot 270 of the ratio of the actual ammonia storage capacity of the SCR catalyst 50 at a given temperature for the first conditions 250 and the second conditions 254 and the plot 274 of the ratio between the target ammonia storage state of the SCR catalyst 50 and the storage capacity of the SCR catalyst 50 at the given temperature. In the illustrated embodiment, the ratio between the target ammonia storage state of the SCR catalyst 50 and the storage capacity of the SCR catalyst 50 is less than 1.0. As can be seen in FIG. 8, a ratio between an actual amount of bound ammonia and a target amount of bound ammonia is higher for the engine operating under the first conditions 250 than the engine operating under the second conditions 254 during the time period ranging between 0 seconds and approximately 700 seconds, which is the time period in which the rate of cumulative vehicle outlet exhaust NOx generated under the first conditions 250 increases the most relative to the cumulative vehicle outlet exhaust NOx generated under the second conditions 254. Since an amount of bound ammonia is inversely correlated with temperature, the first operating conditions 250 have less bound ammonia than the second conditions 254. Accordingly, an amount of bound ammonia can impact NOx conversion.

[0085] In any disclosed embodiment, the term "approximately" may be substituted with "within a percentage of ' what is specified, where the percentage includes 0.1 1, 5, and 10 percent.

[0086] No claim element herein is to be construed under the provisions of 35 U.S.C. § 1140, unless the element is expressly recited using the phrase "means for." [0087] For the purpose of this disclosure, the term "coupled" means the joining or linking of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. For example, a propeller shaft of an engine "coupled" to a transmission represents a moveable coupling. Such joining may be achieved with the two members or the two members and any additional intermediate members. For example, circuit A "coupled" to circuit B may signify that circuit A communicates directly with circuit B (i.e., no intermediary) or communicates indirectly with circuit B (e.g., through one or more intermediaries).

[0088] While various circuits with particular functionality are shown in FIG. 2, it should be understood that the controller 26 may include any number of circuits for completing the functions described herein. For example, the activities and functionalities of the circuits 114 -126 may be combined in multiple circuits or as a single circuit. Additional circuits with additional functionality may also be included. Further, the controller 26 may further control other activity beyond the scope of the present disclosure.

[0089] As mentioned above and in one configuration, the "circuits" may be implemented in machine-readable medium for execution by various types of processors, such as the processor 106 of FIG. 2. An identified circuit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the circuit. Indeed, a circuit of computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within circuits, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.

[0090] While the term "processor" is briefly defined above, the term "processor" and "processing circuit" are meant to be broadly interpreted. In this regard and as mentioned above, the "processor" may be implemented as one or more general-purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs), or other suitable electronic data processing components structured to execute instructions provided by memory. The one or more processors may take the form of a single core processor, multi-core processor (e.g., a dual core processor, triple core processor, quad core processor, etc.), microprocessor, etc. In some embodiments, the one or more processors may be external to the apparatus, for example, the one or more processors may be a remote processor (e.g., a cloud based processor). Alternatively or additionally, the one or more processors may be internal and/or local to the apparatus. In this regard, a given circuit or components thereof may be disposed locally (e.g., as part of a local server, a local computing system, etc.) or remotely (e.g., as part of a remote server such as a cloud based server). To that end, a "circuit" as described herein may include components that are distributed across one or more locations.

[0091] Although the diagrams herein may show a specific order and composition of method steps, the order of these steps may differ from what is depicted. For example, two or more steps may be performed concurrently or with partial concurrence. Also, some method steps that are performed as discrete steps may be combined, steps being performed as a combined step may be separated into discrete steps, the sequence of certain processes may be reversed or otherwise varied, and the nature or number of discrete processes may be altered or varied. The order or sequence of any element or apparatus may be varied or substituted according to alternative embodiments. All such modifications are intended to be included within the scope of the present disclosure as defined in the appended claims. Such variations will depend on the machine-readable media and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure.

[0092] The foregoing description of embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from this disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and its practical application to enable one skilled in the art to utilize the various embodiments and with various modifications as are suited to the particular use contemplated. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present disclosure as expressed in the appended claims.

[0093] Accordingly, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

WHAT IS CLAIMED IS: 1. A system, comprising: a controller structured to: receive information indicative of a storage capacity of a selective catalytic reduction (SCR) catalyst; determine a difference between the ammonia storage capacity of the SCR catalyst and a target ammonia storage state; compare the difference to a difference threshold; receive information indicative of a space velocity through the SCR catalyst; compare the information indicative of the space velocity through the SCR catalyst to a space velocity threshold; and responsive to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold, command an engine to operate according to low nitrous oxide (NOx) combustion parameters; and responsive to the difference being at or below the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold, command the engine to operate according to high NOx combustion parameters.
2. The system of claim I, wherein commanding the engine to operate according to the high NOx combustion parameters generates exhaust having a higher NOx concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.
3. The system of claim 1 or claim 2, wherein the low NOx combustion parameters include at least a first plurality of fuel pressure values and a first plurality of fuel injection values and wherein the high NOx combustion parameters include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.
4. The system of any preceding claim, wherein the space velocity is indicative of an amount of time the exhaust is exposed to the SCR catalyst.
5. The system of any preceding claim, wherein the controller is further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.
6. The system of any preceding claim, wherein the target ammonia storage state is based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof
7. An apparatus, comprising: a selective catalytic reduction (SCR) storage circuit structured to: receive information indicative of a storage capacity of a SCR catalyst and to determine a difference between the information indicative of the storage capacity of the SCR catalyst and a target ammonia storage state; and compare the difference to a difference threshold; a SCR space velocity circuit structured to receive information indicative of a space velocity through the SCR catalyst and compare the information indicative of the space velocity through the SCR catalyst to a space velocity threshold; and an engine operation circuit structured to command an engine to operate according to low NOx combustion parameters or high NOx combustion parameters based on the comparison.
8. The apparatus of claim 7, wherein the engine operation circuit is structured to command the engine to operate according to the low NOx combustion parameters in response to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold.
9. The apparatus of claim 7 or claim 8, wherein the engine operation circuit is structured to command the engine to operate according to the high NOx combustion parameters in response to the difference being less than or equal to the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold.
10. The apparatus of any of claims 7 to 9, wherein commanding the engine to operate according to the high NOx combustion parameters generates exhaust having a higher nitrous oxide (NOx) concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.
11. The apparatus of any of claims 7 to 10, wherein the low NOx combustion parameters include at least a first plurality of fuel pressure values and a first plurality of fuel injection values and wherein the high NOx combustion parameters include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.
12. The apparatus of any of claims 7 to 11, wherein the space velocity is indicative of an amount of time the exhaust is exposed to the SCR catalyst.
13. The apparatus of any of claims 7 to 12, wherein the controller is further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.
14. The apparatus of any of claims 7 to 13, wherein the target ammonia storage state is based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof
15. A method, comprising: receiving information indicative of a storage capacity of a selective catalytic reduction (SCR) catalyst; receiving information indicative of a space velocity through the SCR catalyst; determining a difference between the information indicative of the storage capacity of the SCR catalyst to a target ammonia storage state; comparing the difference to a difference threshold; comparing the information indicative of the space velocity through the SCR catalyst to a space velocity threshold; and commanding an engine to operate according to low NOx combustion parameters in response to at least one of the difference exceeding the difference threshold and the information indicative of the space velocity exceeding the space velocity threshold; and commanding the engine to operate according to high NOx combustion parameters in response to the difference being at or below the difference threshold and the information indicative of the space velocity being less than or equal to the space velocity threshold.
16. The method of claim 15, wherein commanding the engine to operate according to the high NOx combustion parameters generates exhaust having a higher nitrous oxide (NOx) concentration than exhaust generated in response to commanding the engine to operate according to the low NOx combustion parameters.
17. The method of claim 15 or claim 16, wherein the low NOx combustion parameters include at least a first plurality of fuel pressure values and a first plurality of fuel injection values and wherein the high NOx combustion parameters include at least a second plurality of fuel pressure values and a second plurality of fuel injection values.
18. The method of any of claims 15 to 17. wherein the space velocity is indicative of an amount of time the exhaust is exposed to the SCR catalyst.
19. The method of any of claims 15 to 18. wherein the controller is further structured to command the engine to operate according to an engine intake airflow rate predicted based at least on one of the information indicative of the storage capacity of the SCR catalyst and the information indicative of the space velocity through the SCR catalyst.
20. The method of any of claims 15 to 19, wherein the target ammonia storage state is based on at least one of an amount of ammonia bound to the SCR catalyst, an amount of NOx that the ammonia bound to the SCR catalyst can absorb, the temperature of the SCR catalyst, or any combination thereof