Device, method and system for reducing NOx emissions in an SCR catalyst

Abstract

Device for reducing NO x -Emissions in an engine exhaust stream of an engine system with a selective catalytic reduction system having an SCR catalyst (152) positioned downstream of a reducing agent injector (192), comprising: a NO x -Reduction setpoint module (300) that is configured to be NO x -reduction requirement to determine, whereby the NO x -Reduction requirement: an amount of NO to be reduced on the SCR catalyst (152) x in the exhaust gas stream, and a reducing agent module (330) configured to determine the amount of reducing agent to be added to the exhaust gas stream in order to reduce the NO x -To meet the reduction requirement, wherein an amount of reducing agent added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst (152), at least one reducing agent-to-ammonia conversion characteristic and a conversion capability of an AMOX catalyst (160) in exhaust gas receiving communication with the SCR catalyst (152).

Description

[0001] The present disclosure relates to the control or regulation of nitrogen oxide (NOx) emissions. x ) for internal combustion engines and in particular devices, systems and methods for controlling or regulating NO x with a catalyst with selective catalytic reduction (SCR - Selective Catalytic Reduction).

[0002] The present invention relates firstly to a device for reducing NO x -Emissions in an engine exhaust stream of an engine system according to claim 1. Furthermore, the invention relates to a method for reducing NO x -Emissions in an engine exhaust stream of an engine system according to claim 8. Finally, the present invention relates to an engine system with a corresponding SCR system according to claim 11.

[0003] Over the past few years, emissions regulations for combustion engines have become increasingly stringent. The legal emissions of NOₓ x And particulate matter from combustion engines is so low that, in many cases, emission levels cannot be met with improved combustion technologies. Therefore, the use of aftertreatment systems on engines to reduce emissions is increasing. To reduce NO x NOx emissions are reduced using NOx reduction catalysts, including SCR systems, to convert NOx (NO and NO2 in some proportion) into N2 and other compounds. SCR systems use a reducing agent, usually ammonia, to reduce the NO. x to reduce. Currently available SCR systems can produce high NOₓ emissions. x-conversion rates can be achieved, allowing combustion technologies to focus on performance and efficiency. However, currently available SCR systems also have a few shortcomings.

[0004] SCR systems generate ammonia to reduce NOₓ x to reduce NO. When the right amount of ammonia is available at the SCR catalyst under the right conditions, the ammonia is used to reduce NO. xused. However, if the reduction reaction rate is too slow, or if there is excess ammonia in the exhaust gas, ammonia can escape from the exhaust pipe. Ammonia is an extreme irritant and an undesirable emission. Accordingly, even a slip or escape of just a few dozen ppm is problematic. Because handling pure ammonia is undesirable, many systems can additionally use an alternative compound such as urea, which evaporates in the exhaust stream and decomposes into ammonia. Currently available SCR systems treat injected urea as injected ammonia and do not account for the evaporation and hydrolysis of urea into component compounds such as ammonia and isocyanic acid. Consequently, the urea can decompose into ammonia downstream of the SCR, causing ammonia slip, which is problematic for NOₓ. x-Reduction may result in less ammonia being available than the control mechanism estimates, leading to higher NO levels. x -Emissions caused at the tailpipe.

[0005] SCR systems that use urea dosing to generate ammonia are based on the real-time supply of urea to the SCR catalyst, while engine NO x Emissions occur. Compared to other chemical injectors, such as hydrocarbon injectors, urea dosing systems have a relatively slow physical dynamic. Therefore, the dynamics of the urea dosing system can significantly influence an SCR control system.

[0006] Some currently available SCR systems take into account the dynamics of urea dosing and the generally rapid transient nature of the internal combustion engine by utilizing the inherent ammonia storage capacity of many SCR catalyst formulations.

[0007] A currently available method leads to the beginning of an engine NO x -Adds a time delay before the urea dosing begins (or ramps up), and a time delay after the NO x -peak before the urea dosing ends (or decreases). Typically, a motor NO causes x A peak temperature rise in the exhaust gas and the SCR catalyst can lead to the release of stored ammonia from the catalyst. This is especially true when the engine power output is used as a substitute for directly estimating engine NOₓ. x -Emissions are used. The ammonia release provides ammonia to reduce engine-off NOₓ. x , while delaying the urea injection prevents excess ammonia from escaping from the exhaust. With the NO x-Depending on the engine, the temperature of the exhaust gas and the SCR catalyst normally decreases, and therefore continued urea injection (the delay before shutting off the urea injection) provides ammonia to be stored at the SCR catalyst and charges the catalyst.

[0008] In many ordinary circumstances, the time-delay method causes undesirable results in the SCR catalyst. In some cases, however, the time-delay method can produce undesirable results and even reactions that are contrary to an optimal response. For example, a decrease in the EGR fraction for any reason will cause engine stalling. x -Peak with a decrease in exhaust gas temperature. In a time-delay system that uses engine shutdown power as a substitute for NO. x -emissions, the change will likely be ignored and a standard amount of injected urea will result in an increase in NO. x-cause emissions. With a time delay system that controls the engine shutdown NO x If the peak is detected, the system delays the injection of ammonia-producing urea. Because the temperature at the SCR catalyst is relatively lower, the amount of NO released by the catalyst is reduced. x -reducing ammonia, resulting in NO x This leads to an increase in emissions. At the end of the NO x -At the peak event, the exhaust gas temperature rises (from the point of restoration of the designed EGR fraction), while the NO x Emissions decrease. The SCR catalyst releases ammonia from its reduced storage capacity, while the urea injector continues to supply ammonia to the system without NO. x available for reduction. Therefore, significant amounts of ammonia can escape from the system during the downward cycle.

[0009] Other currently available systems determine whether the SCR catalyst is at a temperature that stores ammonia (adsorption) or releases ammonia (desorption). While the SCR catalyst is storing ammonia, the system injects urea until the catalyst is saturated. When the SCR catalyst is releasing ammonia, the system stops the injection and allows the stored ammonia and NOₓ to be released. x reduced.

[0010] Current systems that monitor SCR catalyst temperature have several shortcomings. For example, the amount of ammonia stored on the SCR catalyst varies with temperature. However, currently available systems assume a certain amount of storage below a specified temperature and zero storage above it. Therefore, the controllers can switch significantly around the specified temperature, significantly overestimating the ammonia storage capacity just below and significantly underestimating it just above. Such systems determine the baseline urea injection using the normalized stoichiometric ratio (NSR), but they do not account for variations in NOₓ concentration. x-composition and the NH3-to-isocyanic acid ratio of the urea when determining the NSR. Furthermore, such systems do not account for the incomplete vaporization and hydrolysis of urea that occurs in many systems and therefore may not inject enough urea to produce NO. x to reduce, and / or provide the desired ammonia for storage.

[0011] Furthermore, many well-known SCR systems do not use an ammonia oxidation catalyst (AMOX) downstream of the SCR catalyst to convert at least some of the ammonia escaping from the SCR catalyst into N2 and less harmful compounds. For those conventional SCR systems that do use an AMOX catalyst, the operating conditions and the conversion capability of the AMOX catalyst depend on the reducing agent dosing rate, ammonia storage control, ammonia slip control, and NO2 emissions. x-Conversion efficiency feedback coupling of such systems not taken into account.

[0012] From the prior art, from which the invention is based (DE 103 740 132 A1), a device for reducing NO is available. x -Emissions in an engine exhaust stream of an engine system are known, which has an SCR catalyst positioned downstream of a reducing agent injector. This reduces NO xEmissions in the exhaust stream in the presence of ammonia. This device is controlled within the engine system containing it by a controller. This controller comprises a control unit operating with assumptions and a control unit operating with actual values. Based on operating conditions, the controller selects between the two control units to generate the control signal for the reducing agent injector. The control strategy for selecting the control unit responsible for injection is the subject of this publication.

[0013] The teaching of the present invention is based on the problem of improving the effectiveness of NO reduction in the known device, the known method and the known engine system. x -to further improve emissions.

[0014] The problem identified above is initially solved by a device having the features of claim 1. Preferred embodiments and further developments of these devices are the subject of the dependent claims relating to the device.

[0015] The problem identified above is also solved by a method according to claim 8. Preferred embodiments and further developments of the method according to the invention are the subject of the dependent claims relating to the method.

[0016] Finally, the problem identified above is also solved by the motor system of claim 11. Preferred embodiments and further developments of the motor system according to the invention are the subject of the dependent claims relating to the system.

[0017] Accordingly, the subject matter of the present application was developed to provide devices, methods and systems for reducing NO. x-to provide emissions on an SCR catalyst that overcomes at least some of the shortcomings of state-of-the-art aftertreatment systems.

[0018] According to the invention, a device for reducing NO comprises x -Emissions in an engine exhaust stream of an engine system with an SCR system (Selective Catalytic Reduction) with an SCR catalyst positioned downstream of a reducing agent injector, a NO x -Reduction target module and a reducing agent module. The NO x -Reducing agent setpoint module is configured, a NO x -To determine the reduction requirement, which specifies the amount of NO to be reduced on the SCR catalyst. x in the exhaust gas stream. The reducing agent module is configured to determine the amount of reducing agent to be added to the exhaust gas stream in order to reduce the NO. x-Reduction requirement to be met. The amount of reducing agent added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst, at least one reducing agent-to-ammonia conversion characteristic, and a conversion capability of an AMOX catalyst in exhaust gas-receiving communication with the SCR catalyst.

[0019] In some implementations, the at least one ammonia storage characteristic includes an estimated amount of ammonia stored on the SCR catalyst, an estimated amount of ammonia escaping from the SCR catalyst, and / or an estimated maximum ammonia storage capacity of the SCR catalyst. In some implementations, the at least one reducing agent-to-ammonia conversion characteristic includes the distance between the SCR catalyst and the reducing agent injector, the conversion efficiency of the reducing agent to ammonia, and / or the conversion efficiency of the reducing agent to components other than ammonia. In still other implementations, the conversion capability of the AMOX catalyst is a function of the AMOX catalyst temperature, an AMOX catalyst degradation factor, and / or a target tailpipe ammonia slip.

[0020] According to one implementation, the amount of reducing agent added to the exhaust gas stream is a function of the (physical) state of the SCR catalyst. The physical state of the SCR catalyst can be determined by a degradation factor of the SCR catalyst and / or a maximum NO x -Conversion efficiency of the SCR catalyst can be shown.

[0021] In certain cases, the device also includes an on-board diagnostic module configured to determine if a maximum NO x -Reduction efficiency of the SCR catalyst is below a predetermined threshold.

[0022] According to the invention, a method for reducing NO includes x -Emissions in an engine exhaust stream of an engine system flowing from an engine of the engine system to a tailpipe of the engine system, wherein the engine system has an SCR catalyst and a urea injector upstream of the SCR catalyst, determining an NO x-Reduction requirement. The NO x The reduction requirement includes NO to be reduced on an SCR catalyst. x -Quantity in the exhaust gas stream. The procedure also includes determining the AMOX catalyst conversion capability, the ammonia storage modifier, and the ammonia supplement requirement.

[0023] The ammonia supplement requirement represents the amount of ammonia added to the exhaust gas stream to reduce NOₓ. xThe method involves determining the urea-to-ammonia and urea-to-isocyanic acid conversion factors and determining a urea injection requirement. This requirement is based at least partially on the urea-to-ammonia and urea-to-isocyanic acid conversion factors. Furthermore, the urea injection requirement specifies the amount of urea added to the exhaust gas stream to meet the ammonia reduction requirement. The method also includes determining whether at least one urea-limiting condition is met and modifying the urea injection requirement if it is. Furthermore, the process includes injecting urea into the exhaust gas stream according to the urea injection requirement.

[0024] In some implementations, the ammonia storage modifier is based at least partially on the estimated amount of ammonia stored on the SCR catalyst, the estimated amount of ammonia escaping from the SCR catalyst, and the estimated maximum ammonia storage capacity of the SCR catalyst. In still other implementations, the urea-to-ammonia and urea-to-isocyanic acid conversion factors are based at least partially on the distance between the SCR catalyst and the urea injector, a urea-to-ammonia conversion efficiency, and a urea-to-isocyanic acid conversion efficiency.

[0025] According to the invention, an engine system comprises an internal combustion engine that generates an exhaust gas stream, an SCR system comprising an SCR catalyst that reduces NO xEmissions in the exhaust stream are reduced in the presence of ammonia, and a reducing agent injector injects reducing agent into the exhaust stream upstream of the SCR catalyst, with the reducing agent supplying the ammonia. The engine system also includes a positive feedback component, a feedback-type component, and an ammonia storage component. The positive feedback component is configured to deliver a reducing agent dosing rate according to a desired NOₓ level. x-reduction on the SCR catalyst during steady-state operating conditions of the internal combustion engine. The feedback-type component is configured to modify the reducing agent dosing rate based at least partially on the physical degradation of the SCR catalyst. The ammonia storage component is configured to modify the reducing agent dosing rate based at least partially on a desired ammonia storage concentration on the SCR catalyst. The desired ammonia storage concentration is one that is at least sufficient to compensate for various transient changes in NOₓ. x -Emissions during transient operating conditions of the internal combustion engine must be taken into account.

[0026] In some implementations, the engine system also includes an AMOX catalyst downstream of the SCR catalyst. Consequently, the feedback-type component can be further configured to modify the reducing agent dosing rate based at least partially on the physical degradation of the AMOX catalyst. The desired ammonia storage concentration can be based at least partially on maximizing the ammonia storage capacity of the SCR catalyst and maximizing the NH3 conversion capacity of the AMOX catalyst.

[0027] In some implementations, the reducing agent is urea, which is partially reduced to ammonia and partially to isocyanic acid before entering the SCR catalyst. The urea dosing rate can be based, at least in part, on a first conversion efficiency of urea to ammonia and a second conversion efficiency of urea to isocyanic acid.

[0028] In some implementations, the feedback-type component is further configured to modify the reducing agent dosing rate based at least partially on the occurrence of at least one reducing agent limiting condition. The at least one reducing agent limiting condition may include an exhaust gas temperature limit, an ammonia slip limit, and / or an SCR catalyst bed temperature limit.

[0029] According to some implementations, the desired ammonia storage concentration is based at least partially on the SCR catalyst having the largest possible ammonia storage capacity.

[0030] In certain implementations, the controller includes an on-board diagnostics (OBD) component configured to determine whether the SCR system is capable of maintaining the NO x-Emissions in the exhaust stream to a quantity below a predetermined threshold. The engine system may also include an OBD interface that can communicate electrically with the controller. Consequently, in specific cases, the controller alerts the OBD interface if the OBD component determines that the SCR system is unable to reduce the NOₓ emissions. x -Reducing emissions in the exhaust stream to a level below the predetermined threshold. Determining whether the SCR system is capable of reducing the NO x Reducing emissions in the exhaust stream to a quantity below a predetermined threshold can be based, at least in part, on the physical degradation of the SCR catalyst.

[0031] In some implementations, the SCR system contains NO embedded in the SCR catalyst. x-Sensor. The SCR catalyst can contain a pair of spaced catalyst beds that extend along the length of the SCR catalyst and define a space between the beds. The embedded NO x The sensor can be positioned at least partially in the space between the beds.

[0032] Throughout this specification, a reference to features, advantages, or similar language does not imply that all of the features and advantages that can be realized with the subject matter of this disclosure should be, or are, present in any single embodiment. Rather, language relating to features and advantages is intended to mean that a specific feature, advantage, or characteristic, described in connection with an embodiment, is present in at least one embodiment of this disclosure. Thus, throughout this specification, a discussion of features and advantages and similar language may refer to the same embodiment, but need not.

[0033] Furthermore, the described features, advantages, and characteristics of the subject matter of this disclosure can be combined in any suitable way in one or more embodiments. The person skilled in the art recognizes that the subject matter can be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in certain embodiments that are not present in all embodiments. These features and advantages will become more fully apparent from the following description and the appended claims, or can be ascertained by practicing the subject matter as set forth below.

[0034] To better understand the advantages of the subject matter, a more detailed description of the subject matter briefly described above is provided by reference to specific embodiments illustrated in the accompanying drawings. It is understood that these drawings represent only typical embodiments of the subject matter and should therefore not be considered as limiting its scope of protection. The subject matter is described and explained with additional specificity and detail through the use of these drawings. They show: Fig. 1 a schematic block diagram of an internal combustion engine with an exhaust aftertreatment system according to a representative embodiment; Fig. 2 a schematic block diagram of the exhaust aftertreatment system of Fig. 1 according to a representative embodiment; Fig. 3 A schematic block diagram of a controller for the exhaust aftertreatment system of Fig. 2 according to a representative embodiment; Fig. 4 a schematic block diagram of a NO x -Reduction module of the controller of Fig. 3 according to a representative embodiment; Fig. 5A a schematic block diagram of a positive-feedback ammonia setpoint module of the controller from Fig. 3 according to a representative embodiment; Fig. 5B a schematic block diagram of a feedback ammonia setpoint module of the controller of Fig. 3 according to a representative embodiment; Fig. 6 a schematic block diagram of a reducing agent setpoint module of the controller of Fig. 3 according to a representative embodiment; Fig. 7 a schematic block diagram of a reducing agent hydrolysis module of the reducing agent target module of Fig. 6 according to a representative embodiment; Fig. 8 a schematic block diagram of an inverse reducing agent hydrolysis module of the reducing agent target module of Fig. 6 according to a representative embodiment, Fig. 9 a schematic flow diagram of a control system which can be operated to determine the ammonia and isocyanic acid flow into an SCR catalyst according to an embodiment; Fig. 10 a schematic block diagram of an ammonia storage module of the controller of Fig. 3 according to a representative embodiment; Fig. 11 a schematic block diagram of a current ammonia storage concentration module of the ammonia storage module of Fig. 10 according to a representative embodiment; Fig. 12 a schematic flow diagram of a control system that can be operated to determine the storage concentration of ammonia on an SCR catalyst; Fig. 13 a schematic flow diagram of a control system that can be operated to determine the extent of ammonia slip from an SCR catalyst; Fig. 14 a schematic block diagram of an AMOX catalyst ammonia conversion module of the controller of Fig. 3 according to a representative embodiment; Fig. 15 a schematic block diagram of a reducing agent modifier module of the controller of Fig. 3 according to a representative embodiment; Fig. 16 a schematic block diagram of a corrected tailpipe NO x -module of the reducing agent modifier module of Fig. 15 according to a representative embodiment and Fig. 17 a method for reducing NO x -Emissions using an ammonia storage system on an SCR catalyst.

[0035] Many of the functional units described in this specification have been designated as modules, particularly to emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, commercially available semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field-programmable gate arrays, programmable array logic, programmable logic devices, or the like.

[0036] Modules can also be implemented in software for execution by different types of processors. An identified module of executable code can, for example, comprise one or more physical or logical blocks of computer instructions, which may be organized as an object, a procedure, or a function. However, the executable files of an identified module do not need to be physically located together; they can comprise disparate instructions stored in different locations which, when logically connected, comprise the module and achieve its stated purpose.

[0037] In fact, a module of executable code can be a single instruction or many instructions, and can even be distributed across several different code segments, across different programs, and across multiple memory devices. Similarly, operational data can be identified and represented within modules and can be embodied in any suitable form and organized in any suitable type of data structure. The operational data can be collected as a single data record or can be distributed across different locations, including different memory devices, and can exist, at least in part, simply as electronic signals on a system or network.

[0038] References in this specification to "an embodiment" or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, all occurrences of the expressions "in an embodiment" and similar language in this specification may, but do not necessarily, refer to the same embodiment.

[0039] Furthermore, the described features, structures, or characteristics of the subject matter described herein can be combined in any suitable manner in one or more embodiments. Numerous specific details are presented in the following description, such as examples of controls, structures, algorithms, programming, software modules, user selection, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments of the subject matter. However, the person skilled in the art recognizes that the subject matter can be implemented without one or more of the specific details or with other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the disclosed subject matter. Internal combustion engine system

[0040] Fig. Figure 1 shows an embodiment of an internal combustion engine system 10. The main components of the engine system 10 include an internal combustion engine 11 and an exhaust aftertreatment system 100 coupled to the engine. The internal combustion engine 11 can be a compression-ignition engine, such as a diesel engine, or a spark-ignition engine, such as a lean-burn gasoline engine. The engine system 10 further includes an air intake 12, an intake manifold 14, an exhaust distributor 16, a turbocharger turbine 18, a turbocharger compressor 20, temperature sensors (e.g., temperature sensor 24), pressure sensors (e.g., pressure sensor 26), and an airflow sensor 56. The air intake 12 is vented to the atmosphere and connected to an inlet of the intake manifold 14 to allow air to enter the intake manifold. The intake manifold 14 contains an outlet which is operatively coupled to compression chambers of the internal combustion engine 11 to introduce air into the compression chambers.

[0041] Inside the internal combustion engine 11, air from the atmosphere is combined with fuel to power the engine. The combustion of the fuel and air produces exhaust gas, which is operatively vented to the exhaust manifold 16. From the exhaust manifold 16, a portion of the exhaust gas can be used to drive the turbocharger turbine 18. The turbine 18 drives the turbocharger compressor 20, which can compress at least a portion of the air entering the air inlet 12 before it is directed to the intake manifold 14 and into the compression chambers of the engine 11.

[0042] The exhaust aftertreatment system 100 is coupled to the exhaust manifold 16 of the engine 11. At least a portion of the exhaust gas exiting the exhaust manifold 16 can pass through the exhaust aftertreatment system 100. In certain implementations, the engine system 10 includes an exhaust gas recirculation (EGR) valve (not shown) configured to open so that a portion of the exhaust gas can recirculate back into the compression chambers to modify the combustion characteristics of the engine 11.

[0043] In general, the exhaust aftertreatment system 100 is configured to eliminate various emissions of chemical compounds and particles present in the exhaust gas received by the exhaust distributor 16 and not recirculated to the engine 11. As in Fig. As shown in Figure 2, the exhaust aftertreatment system 100 includes a controller 130, an oxidation catalyst 140, a particulate matter (PM) filter 142, an SCR system 150 with an SCR catalyst 152, and an ammonia oxidation catalyst (AMOX) 160. Exhaust gas can flow from the exhaust distributor 16 through the oxidation catalyst 140, the particulate filter 142, the SCR catalyst 152, and then through the AMOX catalyst 160 in an exhaust gas flow direction indicated by the direction arrow 144, and then be expelled into the atmosphere. In other words, the particulate filter 142 is positioned downstream of the oxidation catalyst 140, the SCR catalyst 152 is positioned downstream of the particulate filter 142, and the AMOX catalyst 160 is positioned downstream of the SCR catalyst 152. In general, the exhaust gas treated in the exhaust aftertreatment system 100 and released into the atmosphere consequently contains significantly fewer contaminants such as diesel particulates and NOₓ.x , hydrocarbons such as carbon monoxide and carbon dioxide, as untreated exhaust gas.

[0044] The oxidation catalyst 140 can be any of the various flow-through diesel oxidation catalysts (DOCs) known in the industry. Generally, the oxidation catalyst 140 is configured to oxidize at least some particulate matter, for example, the soluble organic fraction of soot, in the exhaust gas and to reduce unburned hydrocarbons and CO in the exhaust gas to less harmful compounds. For example, the oxidation catalyst 140 can sufficiently reduce the hydrocarbon and CO concentrations in the exhaust gas to meet the required emission standards.

[0045] The particulate filter 142 can be any of the various particulate filters known in the industry, configured to reduce the concentration of particulate matter, such as soot and ash, in the exhaust gas in order to meet required emission standards. The particulate filter 142 can be electrically coupled to a controller, such as the controller 130, which controls various characteristics of the particulate filter, such as the timing and duration of filter regeneration events.

[0046] The SCR system 150 includes a reducing agent supply system 151, which comprises a reducing agent source 170, a pump 180, and a supply mechanism 190. The reducing agent source 170 can be a container or tank that can hold a reducing agent such as ammonia (NH3), urea, diesel fuel, or diesel oil. The reducing agent source 170 is in a reducing agent supply communication with the pump 180, which is configured to pump reducing agent from the reducing agent source to the supply mechanism 190. The supply mechanism 190 can include a reducing agent injector, shown schematically in Figure 192, positioned upstream of the SCR catalyst 152. The injector can be selectively controlled to inject reducing agent directly into the exhaust gas stream before it enters the SCR catalyst 152.In some formulations, the reducing agent can be either ammonia or urea, which decomposes to produce ammonia. As described in more detail below, in these formulations the ammonia reacts with NO. X in the presence of the SCR catalyst 152, to reduce the NO X to reduce emissions to less harmful substances such as N2 and H2O. The SCR catalyst 152 can be any of the various catalysts known in the art. For example, in some implementations, the SCR catalyst 152 is a vanadium-based catalyst, and in other implementations, the SCR catalyst is a zeolite-based catalyst such as a Cu-zeolite or an Fe-zeolite catalyst. In one representative embodiment, the reducing agent is aqueous urea, and the SCR catalyst 152 is a zeolite-based catalyst.

[0047] The AMOX catalyst 160 can be any of several different flow-through catalysts configured to react with ammonia and primarily produce nitrogen. Generally, the AMOX catalyst 160 is used to eliminate ammonia that has passed through or escaped from the SCR catalyst 152 without reacting with NO. x to react in the exhaust gas. Under certain circumstances, the system 10 can be operated with or without an AMOX catalyst. Although the AMOX catalyst 160 is shown as a separate unit from the SCR catalyst 152, in some implementations the AMOX catalyst can still be integrated with the SCR catalyst; for example, the AMOX catalyst and the SCR catalyst can be located within the same housing.

[0048] The exhaust aftertreatment system 100 contains various sensors, such as temperature sensors 124A-F, pressure sensors 126, oxygen sensor 162, NOx -Sensors 164A-D, NH3 sensors 166A-C, dual ammonia / NO sensors not shown x Sensors and the like are arranged in the exhaust aftertreatment system. The various sensors can communicate electrically with the controller 130 to monitor operating conditions and to control the engine system 10, including the exhaust aftertreatment system 100. In the illustrated embodiment, the exhaust aftertreatment system 100 includes the NO x -Sensor 164A upstream of the oxidation catalyst 140, the NO coupled to or embedded in a central section of the SCR catalyst 152 x -Sensor 164B, the No. x -Sensor 164C between the SCR catalyst and the AMOX catalyst 160, the NO x -Sensor 164D behind the AMOX catalyst and the NO x-Sensor 164E behind the PM filter 142 and before the reducing agent injector 192. Furthermore, the exhaust aftertreatment system 100 shown includes the NH3 sensor 166A before the SCR catalyst 125, the NH3 sensor 166B embedded in the SCR catalyst 152 and the NH3 sensor 166C behind the AMOX catalyst 160.

[0049] Although the exhaust aftertreatment system 100 shown comprises an oxidation catalyst 140, a particulate filter 142, an SCR catalyst 152, and an AMOX catalyst 160 positioned at specific locations relative to each other along the exhaust gas flow path, in other embodiments the exhaust aftertreatment system may include more than one of any of the various catalysts, positioned at any number of different locations relative to each other along the exhaust gas flow path, as desired. Furthermore, while the oxidation catalyst 140 and the AMOX catalyst 160 are non-selective catalysts, in some embodiments the oxidation catalyst and the AMOX catalyst may be selective catalysts.

[0050] The controller 130 controls and regulates the operation of the engine system 10 and the associated subsystems, such as the engine 11 and the exhaust aftertreatment system 100. The controller 130 is in Fig. 2 is represented as a single physical unit, but if desired, in some embodiments it can contain two or more physically separate units or components. Generally, the controller 130 receives multiple inputs, processes the inputs, and transmits multiple outputs. The multiple inputs can include acquiring measurements from the sensors and various user inputs. The controller 130 processes the inputs, using various algorithms, stored data, and other inputs to update the stored data and / or generate output values. The generated output values ​​and / or commands are transmitted to other components of the controller and / or to one or more elements of the engine system 10 to control or regulate the system, achieve desired results, and, in particular, achieve desired exhaust emissions.

[0051] The controller 130 contains various modules for controlling the operation of the engine system 10. For example, the controller 130 contains one or more modules for controlling the operation of the particulate filter 142, as described above. The controller 130 also contains one or more modules for controlling the operation of the SCR system 150. The controller 130 further contains one or more modules for controlling the operation of the engine 11. In addition, if the oxidation catalyst 140 and the AMOX catalyst 160 can be selectively controlled, the controller 130 may contain one or more modules for controlling the operation of the respective oxidation and AMOX catalysts.

[0052] In certain embodiments, the controls of the SCR system 150 include three main components: (1) a positive feedback component designed to calculate a reducing agent dosing rate for steady-state operation of the engine 11; (2) a negative feedback component designed to compensate for the positive feedback component with respect to any long-term degradation of the SCR and AMOX catalyst 152, 160; (3) an ammonia storage component designed to calculate a reducing agent dosing rate required to fill ammonia storage sites on the SCR catalyst 152 to accommodate transient operation of the engine 11. In certain implementations, the negative feedback component may include an SCR catalyst degradation factor module, an NO x -Reduction efficiency module and / or an AMOX-NH3 conversion efficiency module, as described in more detail below.

[0053] With reference to Fig. 3 and according to one embodiment, the controller 130 includes several modules for achieving the above three main components and controlling the operation of the SCR system 150 in order to achieve efficient NO reduction during transient and steady-state operation x to achieve this while reducing ammonia slip from the tailpipe. In particular, the Controller 130 contains a NO x -Reduction setpoint module 300, at least one ammonia setpoint module (e.g., positive-feedback ammonia setpoint module 310 and negative-feedback ammonia setpoint module 344), one reducing agent setpoint module 330, one NH3 storage module 350, one AMOX-NH3 conversion module 380, one reducing agent limiting module 390, and one corrected tailpipe NO x Module 397. In general, the modules are operated independently and / or in cooperation to achieve optimal NO x-to achieve conversion efficiency on the SCR catalyst 152 while minimizing ammonia slip and urea consumption. The controller 130 can communicate in data receiving and / or transmission communication with several subsystems of the engine system 10, such as engine controls 167, PM filter system controls 168 and SCR system controls or regulators 169. NO x -Reduction target module

[0054] With reference to Fig. 4 can the NO x -Reduction target module 300 is operated in such a way as to produce a NO x -Reduction requirement 304 to be determined. The NO x The reduction requirement is set by NO x -represents the amount that should be reduced from the exhaust gas stream on the SCR catalyst 152 in order to achieve a predetermined exhaust emission limit. In other words, the NO determines x -Reduction target module 300 the NO x-Reduction requirement 304, which is necessary to achieve the desired tailpipe NO x -Level 306 to be reached. The desired amount of NO x at the tailpipe, for example, desired tailpipe NO x -Level 306 (see Fig. 4 and Fig. 16), is representative of the NO x -Amount that may escape from the tailpipe according to legally regulated emission standards.

[0055] Generally, the NO x -Reduction requirement 304 as the proportion of NO to be reduced x expressed in the exhaust gas stream. The NO x -Reduction requirement can also be expressed as NO x -reduction rate or the rate at which NO x The amount of NO that should be reduced to meet the predetermined exhaust emission limit can be expressed as follows: In certain implementations, the NO can be expressed as follows: x -Reduction target module 300 in data receiving communication with the NO xSensor 164A communicates to measure the NO present in the exhaust stream. x -amount to be determined before it enters the SCR catalyst 152. Alternatively or additionally, in some implementations, the NO present in the exhaust gas stream can be determined. x The quantity is estimated via the operation of an engine operating condition module 302. The engine operating condition module 302 compares the operating conditions of the engine 11 with a stored operating map that specifies predetermined exhaust NOₓ values. x -Levels for various engine operating conditions are included to provide an estimated NO x -To determine the amount in the exhaust gas stream. The NO x -Reduction target module 300 compares the actual or estimated NO x - Amount in the exhaust gas flow at the engine outlet with a desired NOₓ x -Level 306, in the exhaust gas emitted from the tailpipe, to reduce the NO x -Determine reduction requirement 304. Ammonia target module

[0056] The Controller 130 contains an ammonia setpoint module that can be operated to determine an ammonia supplement requirement. As defined herein, the ammonia supplement requirement is the amount of ammonia that should be added to the exhaust gas stream to reduce the NOₓ. x to reduce the ammonia content in the exhaust gas stream to the desired level in order to meet emission standards. In certain embodiments, the controller 130 includes the feedback ammonia setpoint module 310 for determining an additional ammonia requirement 326 using a feedback methodology (see Fig. 5A). In other embodiments, the controller 130 includes the feedback ammonia setpoint module 344 for determining an additional ammonia requirement 348 using a feedback methodology (see Fig. 5B). In other embodiments, the controller 130 includes both the positive-feedback ammonia setpoint module 310 and the negative-feedback ammonia setpoint module 344.

[0057] First, with reference to Fig. 5A receives the NO input from the positive-coupling ammonia setpoint module 310. x -Reduction requirement 304 from the NO x -Reduction target module 311 (see Fig. 4), an NH3 memory modifier 352 from the NH3 memory module 350 (see Fig. 10) and a current SCR catalyst inlet NH3 flow rate 335 from the reducing agent hydrolysis module 333 (see Fig. 7) and used by module 310 to determine the ammonia setpoint requirement 326. In the representative embodiment shown, the positive-coupling ammonia setpoint module 310 includes an NO x -Reduction efficiency module 312, an SCR catalyst inlet NO2 / NO x -ratio-module 314, an SCR catalyst inlet exhaust gas properties-module 316, an SCR catalyst bed temperature-module 318, an SCR catalyst inlet-NO x -Module 320, an SCR catalyst space velocity module 322 and an NO x-Reduction reaction rate modulus 324.

[0058] The NO x -Reduction efficiency module 312 can be operated in such a way as to maximize the efficiency of the NO x -reduction on the SCR catalyst 152 to be determined. Generally speaking, or rather, determined by the NO x -Reduction efficiency module 312 a desired NO x -Conversion efficiency and the condition of the SCR catalyst.

[0059] At the desired NO x Conversion efficiency can be any of several different efficiencies, and it can depend on the difference between the NO x -Quantity in the exhaust gas flow at the engine outlet and the desired NO x The amount of NO in the exhaust stream at the tailpipe outlet depends on this. For example, in some implementations, the desired NO can be... x -Conversion efficiency of the SCR catalyst 152 is the efficiency required to achieve the desired tailpipe NO at the SCR catalyst outlet.x -level 306 to be achieved. However, in embodiments with an AMOX catalyst, the desired NO can be reached. x -The conversion efficiency of the SCR catalyst 152 will be lower than if no AMOX catalyst is used, because the AMOX catalyst can reduce the ammonia escaping from the SCR catalyst.

[0060] Accordingly, the NO x -Reduction efficiency module 312 is operated in such a way as to achieve the desired NO x -Conversion efficiency with maximum NO x - to compare the conversion efficiency of the SCR catalyst 152 and output the lower of the two efficiencies to the positive-coupling ammonia setpoint module 310. The positive-coupling ammonia setpoint module 310 then uses the lower of the efficiencies generated by the NO x -Reduction efficiency module 312 certain desired and largest NO x -Conversion efficiency to determine the ammonia supplement requirement 326. In general, the smaller NO xThe conversion efficiency is lower the lower the ammonia supplement requirement 326. The NO x -Reduction efficiency module 312 can achieve the largest NO x -Determine the conversion efficiency of the SCR catalyst 152 in different ways.

[0061] The condition of the SCR catalyst 152 influences its efficiency. The more degraded the SCR catalyst, the lower its maximum NO reduction efficiency. x -Reduction on the SCR catalyst 152. The state of the SCR catalyst 152 can also be specified by an SCR catalyst degradation factor. The SCR catalyst degradation factor can be expressed by an SCR catalyst degradation factor module, such as the one below in relation to Fig. Module 368, described in 11, can be determined according to any of the different ways.

[0062] The SCR catalyst inlet NO2 / NO x -ratio-module 314 can be operated, the NO2 / NO x-ratio of the exhaust gas in the exhaust gas stream at the inlet of the SCR catalyst 152 to predict. In some implementations, the NO2 / NO ratio is used. x -ratio expressed as the following ratio: NO2NO+NO2 where NO is the mass concentration of nitrogen monoxide in a predetermined exhaust gas volume and NO2 is the mass concentration of nitrogen dioxide in the predetermined exhaust gas volume.

[0063] The SCR catalyst inlet exhaust gas properties module 316 can be operated to determine various exhaust gas properties at the inlet of the SCR catalyst 152. These properties can include, for example, the exhaust gas mass flow rate and the exhaust gas temperature. In some implementations, the exhaust gas properties are predicted based on predetermined exhaust gas property values ​​for predetermined operating conditions of the engine system 10. For example, the SCR catalyst inlet exhaust gas properties module 316 can include an exhaust gas property map, an exhaust gas property table, or an exhaust gas property vector that compares predetermined exhaust gas property values ​​with engine system operating conditions such as the operating load and / or the engine speed 11.In certain implementations, the SCR catalyst inlet exhaust gas properties module 316 determines the exhaust gas properties by processing an input from any of the various sensors known in the technology, such as mass flow and temperature sensors.

[0064] The SCR catalyst bed temperature module 318 can be used to determine the bed temperature of the SCR catalyst 152. The bed temperature of the SCR catalyst 152 can be determined based on one or more temperature sensors embedded in the SCR catalyst, such as the temperature sensor 124D, or predicted by a module (see, for example, the AMOX catalyst bed temperature module 386). Fig. 13), which uses various operating parameters of the system, such as the exhaust gas mass flow rate and the exhaust gas temperature before and after the SCR catalyst 152. Although the illustrated embodiments use an SCR catalyst bed temperature sensor 124D to determine the temperature of the SCR catalyst bed, in other embodiments the sensor is replaced or supplemented by an SCR catalyst bed temperature module that can be actuated to predict or estimate the temperature of the SCR catalyst bed.

[0065] The SCR catalyst inlet NO x Module 320 can be activated, the concentration of NO x to determine the NO in the exhaust gas at the inlet of the SCR catalyst 152. xThe NO concentration can be predicted based on predetermined exhaust gas conditions according to predetermined operating conditions of the engine system 10. For example, module 320 can access an exhaust gas property map, an exhaust gas property table, or an exhaust gas property vector, such as the one described above, to predict the NO concentration. x -concentration in the exhaust gas. Alternatively or additionally, the concentration of NO can be determined. x in the exhaust gas upon entry into the SCR catalyst 152 using the first NO positioned upstream of the SCR catalyst x -Sensor 164A can be measured.

[0066] The SCR catalyst space velocity module 322 can be activated to determine the space velocity of the SCR catalyst 152. In general, the space velocity of the SCR catalyst 152 represents the NOₓ. xThe space velocity represents the amount of material in the exhaust gas stream that can react within the SCR catalyst over a given time. Accordingly, the space velocity of the SCR catalyst 152 is usually expressed as a unit of time, e.g., 1 / hour, 1000 / hour, etc. The space velocity of the SCR catalyst 152 is based on various exhaust gas and catalyst conditions. For example, the space velocity may be based, at least in part, on the volume and / or reaction or bed, the surface area of ​​the SCR catalyst, and the density, viscosity, and / or flow rate of the exhaust gas. In some implementations, the SCR catalyst space velocity module 322 determines the space velocity of the SCR catalyst 152 by receiving inputs regarding the operating conditions of the engine system 10 and, based on the operating conditions, obtaining the space velocity of the SCR for the given conditions by accessing a table or map stored in the module.The table may contain various predetermined space velocities obtained through experimental testing and calibration for a given SCR catalyst operating under the various operating conditions achievable by the engine system 10.

[0067] The NO x -Reduction reaction rate module 324 can be activated to predict the rate at which ammonia reacts with NO. x reacts on the SCR catalyst 152 and reduces it. The predicted NO x The reaction rate depends at least partially on the NO x -Composition or concentration of the exhaust gas and the frequency of the different types of NO x -Reduction reactions that take place on the SCR catalyst 152. Generally, NO x reduced by ammonia in one of the following three most active stoichiometric chemical reactions: NH3+12NO+12NO2→N2+32H2O NH3+NO+14O2→N2+32H2O NH3+34NO2→78N2+32H2O

[0068] The predicted NO x The reaction rate also depends at least partially on the ammonia concentration rate, the bed temperature of the SCR catalyst 152, and the space velocity of the SCR catalyst. Furthermore, in some implementations, the predicted NO x The reaction rate also depends at least partially on the degradation factor or the condition of the SCR catalyst 152. The predicted NO x The reaction rate can be defined as the sum of a predicted NO x -Reaction rate to reduce NO according to equations 2 and 3 above and a predicted NO x -Reaction rate to reduce NO2 according to equations 3 and 4 above.

[0069] At least partially based on the desired NO x -Conversion efficiency of NO2 / NO x-ratio of the exhaust gas, the exhaust gas flow rate, the temperature and the condition of the bed of the SCR catalyst 152, the amount of NO x and NH3 at the inlet of the SCR catalyst and the NO x The reduction reaction rate determines the ammonia target module and the ammonia additional requirement 326. In some embodiments, the ammonia additional requirement 326 is also based, at least partially, on an NH3 storage modifier 352 determined by an NH3 storage module 350, as will be described in more detail below (see Fig. 7).

[0070] According to a Fig. In the further embodiment shown in Figure 5B, the additional ammonia requirement, e.g., additional ammonia requirement 348, can be determined by the feedback ammonia setpoint module 344. The feedback ammonia setpoint module 344 receives the desired tailpipe NO as input. x-Level 306, the amount of NH3 exiting the tailpipe after detection by the tailpipe NH3 sensor 166C, the NH3 storage modifier 352 and a corrected tailpipe NO x -Value 399 (see Fig. 16). Furthermore, the feedback ammonia setpoint module 344 includes an exhaust gas flow characteristics module 345 and a tailpipe NOₓ module. x -Feedback module 347. In contrast to the positive feedback ammonia setpoint module 310, the feedback ammonia setpoint module 344 is mainly based on the properties of the exhaust gas flow after passing through the SCR catalyst 152 and adjusts the reducing agent dosing rate to compensate for errors and discrepancies in the SCR system 150.

[0071] The exhaust gas flow characteristics module 345 can be operated to determine various states of the exhaust gas flow, e.g. temperature, flow rate, etc., in a manner similar to that described above in relation to the SCR catalyst inlet exhaust gas characteristics module 316.

[0072] The tailpipe NO x -Feedback module 347 can be actuated, an end pipe NO x -To determine the feedback value that can be used by the feedback ammonia setpoint module 344 to determine the ammonia supplementary requirement 348. The tailpipe NO x The feedback value takes into account inconsistencies in the SCR system 150, such as modulation errors, catalyst aging, sensor aging, reductant concentration variations, and reductant injector delays, which can reduce the system's efficiency. Therefore, the tailpipe NOₓ x -Feedback module 396 can be operated, the tailpipe NO x-Feedback value to modulate in order to increase the efficiency of the SCR system 150 and the desired NO x -To achieve conversion efficiency despite inconsistencies that may exist in the system.

[0073] The tailpipe NO x -Feedback module 347 generates the tailpipe NO x -Feedback value by comparing the recorded NO x -Quantity as detected by the tailpipe NO x -Sensor 164D with the desired or targeted tailpipe NO x Quantity 306. Accordingly, the tailpipe NO depends x -Feedback value at least partially based on the difference between the measured tailpipe NO x and the desired or intended tailpipe NO x 306 from. Generally, the greater the difference between the measured tailpipe NO x and the desired tailpipe NO x 306, the greater the additional ammonia requirement 348. If, for example, the measured amount of tailpipe NOx compared to the targeted tailpipe NO x If the value 306 is relatively high, then the feedback ammonia setpoint module 344 can increase the ammonia supplementary requirement 348. As explained in more detail below, an increase in the ammonia supplementary requirement 348 can lead to an increased NO in the exhaust gas flow. x -Conversion on the SCR catalyst 152 requires adding more reducing agent. Conversely, if the amount of tailpipe NO detected x compared to the targeted tailpipe NO x If the 306 is relatively low, then the feedback ammonia setpoint module 344 can lower the ammonia supplement requirement, which can consequently lead to less reducing agent being added to the exhaust gas stream in order to save reducing agent and thus increase the efficiency of the SCR system 150.

[0074] Because of the cross-sensitivity of some NO x-Sensors for ammonia are used in certain embodiments of the SCR system 150 to generate the additional ammonia request only when no ammonia escapes from the SCR system 150, i.e., from the tailpipe. Whether ammonia escapes from the tailpipe can be detected by the tailpipe NH3 sensor 166C and / or predicted by the AMOX-NH3 conversion module 380, as described in more detail below.

[0075] In certain embodiments, the controller 130 includes a control logic selection algorithm (not shown) configured to select one of the ammonia supplement requirements 326 or 348 to act as the ammonia supplement requirement for the SCR system 150, based at least in part on whether NH3 is escaping from the tailpipe. In other words, the module used to determine the ammonia supplement requirement for the SCR system 150 can be switched based on whether the SCR system is operating in a tailpipe NH3 slip mode or a tailpipe NH3 no-slip mode. In particular, if NH3 is escaping from the tailpipe, the ammonia supplement requirement 326 determined by the feedback ammonia setpoint module 310 is reported to the reducing agent setpoint module 330 and used in determining the reducing agent injection requirement 332 (see Fig. 8) Conversely, if no NH3 escapes from the tailpipe, the ammonia supplement request 348, determined by the feedback ammonia setpoint module 344, is reported to the reducing agent setpoint module 330 and used in determining the reducing agent injection request 332. In some implementations, the control logic selection algorithm of the controller 130 determines the ammonia supplement request based on a combination, e.g., an average, of the ammonia supplement requests 326 and 348, regardless of whether ammonia escapes from the tailpipe. In certain implementations, the ammonia supplement request 326 can be adjusted according to the ammonia supplement request 348.

[0076] In some embodiments, the feedback ammonia setpoint module 344 includes a signal correction algorithm (not shown) that is configured to adjust the signal from the tailpipe NO. x -Sensor 164D to filter in such a way that the signal is suitable for a more precise NO x-concentration at the tailpipe when ammonia escapes from the tailpipe. Accordingly, the additional ammonia request 348 generated by the feedback ammonia setpoint module 344 can be reported to the reducing agent setpoint module 330 during operation in the tailpipe NH3 slip or non-slip mode.

[0077] As described above, the controller 130 can determine an ammonia boost request for the SCR system 150 using the positive-feedback ammonia boost module 310, the negative-feedback ammonia boost module 344, or both. After determination, the ammonia boost request, e.g., ammonia boost request 326, ammonia boost request 348, or a combination of both, is reported to the reducing agent boost module 330, or more precisely, to the inverse reducing agent hydrolysis module 334 of the reducing agent boost module. As used below, the ammonia boost request reported to the reducing agent boost module 330 is referred to as ammonia boost request 326. Nevertheless, it can be seen that any reference to the ammonia supplement requirement 326 can be substituted with the ammonia supplement requirement 348 or a combination of the ammonia supplement requirements 326, 348. Reducing agent target module

[0078] With reference to Fig. 6 contains the reducing agent setpoint module 330, a reducing agent hydrolysis module 333, and an inverse reducing agent hydrolysis module 334. As described in more detail below, the reducing agent hydrolysis module 333 can be actuated to determine a current SCR catalyst inlet NH3 flow rate 335 and a current SCR catalyst inlet HNCO flow rate 336 based on the current reducing agent dosing rate (see Fig. 7) The current SCR catalyst inlet NH3 flow rate 335 and the current SCR catalyst inlet HNCO flow rate 336 are then reported to other various modules of the control system 150. In contrast to the reducing agent hydrolysis module 333, the inverse reducing agent hydrolysis module 334 can be actuated to receive the ammonia supplement request 326 from the ammonia setpoint module 310 and determine a reducing agent injection request or dosing rate 332, i.e., the amount of reducing agent required to meet the ammonia supplement request 326 (see Fig. 8) Based on the reducing agent injection request 332, the controller 130 orders the SCR system controls to inject an amount of reducing agent corresponding to the reducing agent injection request 332.

[0079] The reducing agent can be any of the various reducing agents known in engineering. For example, in one implementation, the reducing agent is ammonia. In other implementations, the reducing agent is urea, which decomposes into ammonia and other components, as will be described in more detail below. Reducing agent hydrolysis module

[0080] Again with reference to Fig. 7 The reducing agent hydrolysis module 333 contains an NH3 conversion efficiency table 337, an isocyanic acid (HNCO) conversion efficiency table 338, and an SCR catalyst inlet exhaust gas properties module 339. The SCR catalyst inlet exhaust gas properties module 339 can be actuated to determine the mass flow rate of the exhaust gas stream in a manner similar to that described above in relation to the SCR catalyst inlet exhaust gas properties module 316. Fig. 5 described. The reducing agent hydrolysis module 333 can communicate in data-receiving communication with the reducing agent supply mechanism 190 to receive a current reducing agent dosing rate 383, and with the exhaust gas temperature sensor 124B to receive the temperature of the exhaust gas.

[0081] As described above, in implementations where the reducing agent is urea, the reducing agent hydrolysis module 333 can be operated to determine the amount of ammonia and isocyanic acid entering the SCR catalyst 152. According to one embodiment, the reducing agent hydrolysis module 333 can be operated as shown in the schematic flow diagram 400. Fig. 9 to determine the current SCR catalyst inlet NH3 and HNCO flow rates 335, 336. The exhaust gas temperature is detected or estimated at 410 by temperature sensor 124B, and the exhaust gas mass flow rate is estimated by the SCR catalyst inlet exhaust gas properties module 339 at 420. Based at least partially on the exhaust gas temperature determined at 410 and the exhaust gas mass flow rate determined at 420, the conversion efficiency of urea to NH3 is determined at 430 and the conversion efficiency of urea to isocyanic acid (HNCO) is determined at 440. Accordingly, the conversion efficiencies of urea to NH3 and isocyanic acid are a function of the exhaust gas temperature and the mass flow rate. The NH3 and HNCO conversion efficiencies are determined by comparing the exhaust gas temperature and mass flow rate with one or more predetermined efficiency values ​​found on NH3 and HNCO conversion efficiency reference tables 337 and 338, respectively.

[0082] In accordance with the reducing agent injection request 332 received by the SCR inlet ammonia and isocyanate module 360 ​​from the reducing agent setpoint module 330, urea is injected into the exhaust gas stream by a urea injector at 450. The urea mixes with the exhaust gas stream flowing through an exhaust pipe between the urea injector and the surface of the SCR catalyst 152. As the urea flows along the exhaust pipe, it reacts with the exhaust gas to form NH3 at 460 and HNCO at 470. The NH3 and HNCO in the exhaust gas stream then enter the SCR catalyst 152 as the current SCR catalyst inlet NH3 flow rate 335 and the current SCR catalyst inlet HNCO flow rate 336, respectively. After the HNCO enters the SCR catalyst 152, the catalyst bed promotes a reaction between at least part of the HNCO and water (H2O) in the exhaust gas stream to form additional NH3 at 480.The current SCR catalyst inlet NH3 flow rate 335 and the current HNCO-to-NH3 flow rate 341, i.e., the NH3 from the conversion of HNCO to NH3 taking place within the SCR catalyst 152 at 480, are combined to provide an estimate of the total amount of ammonia within the SCR catalyst, i.e., the current SCR catalyst NH3 flow rate 343. The estimated amount of HNCO that was not converted to NH3 at 480 flows through and out of the SCR catalyst 152 at an SCR catalyst outlet HNCO flow rate 349. As discussed above, the amount of urea converted to NH3 depends at least partially on the NH3 conversion efficiency. In an ideal situation, the NH3 conversion efficiency is 100%, so that all urea is converted into two parts ammonia and one part carbon dioxide without any intermediate conversion to HNCO according to the following equation: NH2-CO-NH2(aq)+H2O→2NH3(g)+CO2 (5)

[0083] In fact, the NH3 conversion efficiency is usually below 100%, so the urea is converted into ammonia and isocyanic acid according to the following equation: NH2-CO-NH2(s) →NH3(g)+HNCO(g) (6)

[0084] The remaining isocyanic acid is converted into ammonia and carbon dioxide (CO2) according to the HNCO conversion efficiency. In ideal conditions, the HNCO conversion efficiency is 100%, so that all isocyanic acid within the SCR catalyst 152 is converted into a portion of ammonia and a portion of carbon dioxide according to the following equation. HNCO(g)+H2O(g) →NH3(g)+CO2(g) (7)

[0085] However, the HNCO conversion efficiency is usually below 100%, so that some of the HNCO is converted into ammonia and carbon dioxide and the remaining part of the HNCO is not converted within the SCR catalyst 152.

[0086] The flow rate of NH3 in the SCR catalyst 152 (ṅ NH3(s)) per flow rate of injected urea (ṅ Harnstoff (s)) is estimated according to the following equation: n˙NH3(s)n˙ureo(s)=1τs+1(1−e−xL)ηNH3(m˙,T) where τ is the mixing time constant, s is a complex variable used for the Laplace transforms, L is the characteristic mixing length, x is the distance from the urea injector to the SCR catalyst inlet or SCR catalyst surface, and η NH3The NH3 conversion efficiency of urea is based on the exhaust gas mass flow rate (ṁ) and temperature (T). The complex variable s can be expressed as σ + jω, where σ is the amplitude and ω is the frequency of a sinusoidal wave associated with a given urea dosing rate input. The mixing time constant is predetermined, at least in part, based on the Heavy Duty Transient Cycle of the FTP (Federal Test Procedure) for emissions testing of high-performance road engines. Assuming a conversion efficiency of 100%, the mixing time constant is matched to the FTP data to eliminate transient mismatches. The characteristic length L is defined as the linear principal dimension of the exhaust pipe, which is substantially perpendicular to the exhaust gas flow. For a cylindrical exhaust pipe, for example, the linear principal dimension is the diameter of the pipe.In some embodiments, the distance from the urea injector to the SCR catalyst surface x is between approximately 5 and 15 times the characteristic length. In specific implementations, the distance x is approximately 10 times the characteristic length.

[0087] Similarly, the flow rate of isocyanic acid (HNCO) into the SCR catalyst 152 (ṅ HNCO (s)) per flow rate of injected urea (ṅ Hamstoff (s)) estimated according to the following equation: n˙HNCO(s)n˙urea(s)=1τs+1(1−e−xL)ηHNCO(m˙,T) where η HNCO The efficiency of the conversion of HNCO from urea is [missing information]. The conversion efficiencies of urea to ammonia (η) NH3 ) and urea to isocyanic acid (η HNCO) is determined in advance based on operating parameters of the engine system 10. In some implementations, the conversion efficiencies are adjusted by comparing a measurement of NH3 and HNCO at the inlet of the SCR catalyst 152 with the expected amount of NH3 and HNCO based on the stoichiometric reaction of equation 6, while urea is metered into the exhaust gas at specific mass flow rates and temperatures. Inverse reducing agent hydrolysis module

[0088] Now with reference to Fig. 8. The inverse reducing agent hydrolysis module 334 of the reducing agent target module 330 can be actuated, at least partially, based on the ammonia target module 310's ammonia target request 326, to determine the reducing agent injection request 332 in order to achieve the ammonia target module 310's ammonia target request 326. In some implementations, the process used by the inverse reducing agent hydrolysis module 334 to determine the reducing agent injection request 332 is similar to the process shown in flowchart 400, but inverted. In other words, the same techniques used in flowchart 400 to determine the current SCR catalyst inlet NH3 flow rate 335 can be used to determine the reducing agent injection request 332, but in a different order.

[0089] For example, in flowchart 400, the actual urea dosing rate is known and is used to determine the NH3 flow rate in the SCR catalyst 152. In contrast, in the process used by the inverse reducing agent hydrolysis module 334, the ammonia addition requirement 326, for example, the desired or estimated NH3 flow rate in the SCR catalyst 152, is known and is used to determine the corresponding reducing agent injection requirement, for example, dosing rate, needed to achieve the desired NH3 flow rate. The reducing agent injection requirement 332 is determined by predicting the hydrolysis rates and conversion efficiencies of urea to NH3 and HNCO based on the temperature and mass flow rate of the exhaust gas stream.For example, the inverse reducing agent hydrolysis module 334 can include an NH3 conversion efficiency table, an HNCO conversion efficiency table, and an SCR catalyst inlet exhaust gas properties module similar to the reducing agent hydrolysis module 333. Alternatively, the inverse reducing agent hydrolysis module 334 can access the NH3 conversion efficiency table 337, the HNCO conversion efficiency table 338, and the output of the SCR catalyst inlet exhaust gas properties module 339 of the reducing agent hydrolysis module 333.

[0090] In some implementations, when the desired flow rate of NH3 into the SCR catalyst is 152 (ṅ NH3 , (s)), e.g. the ammonia supplement requirement, is known, the reducing agent injection requirement 332 from equation 8 above is determined by the flow rate of injected urea ṅ Harnstoff(s) is solved. In a specific implementation, the reduction injection requirement 332, expressed as mL / hr, is approximately equal to: mLhrUrea≈1.85*f(a)*m˙NOx where m NO x equal to the mass flow rate of the NO x -Total quantity in the exhaust gas stream expressed as grams / hour and f(a) is a dimensionless piecewise function where a is equal to the NO2 / NO expressed above in equation 1 x The ratio is... If NO is greater than or equal to NO2, i.e., NO2 / NO x ≤ 0.5, f(a) is approximately equal to one, and if NO is less than or equal to NO2, i.e., NO2 / NO x ≥ 0.5, then f(a) is equal to: 2(a+1)3

[0091] In another specific embodiment, the reduction injection requirement 332 is based on the ideal stoichiometric conversion of urea to ammonia and the ideal stoichiometric reduction of NO. xThe concentration of NO in the exhaust gas stream is determined on the SCR catalyst 152. If the concentration of NO in the exhaust gas stream is greater than or equal to the concentration of NO2 in the exhaust gas, the amount of urea required to reduce one gram of NO is increased. x as shown in Equation 12 below. If the concentration of NO in the exhaust gas is less than or equal to the concentration of NO2 in the exhaust gas, the amount of urea required to reduce one gram of NO x represented by equation 13 below, where a is equal to the NO2 / NO expressed above in equation 1. x -ratio is Harnstoff is, as expressed in equations 12 and 13, the molar weight of the urea to be injected and MW NOx the molecular weight of NO x in the exhaust stream. 0.5*(MWureaMWNOx) 0.5*(MWureaMWNOx)*2(a+1)3

[0092] Based on equations 12 and 13, the flow rate of urea in grams per second can be expressed as the mass flow rate of NO.x (ṁ NOx ) in the exhaust gas stream. For example, if the amount of NO in the exhaust gas stream is greater than or equal to the amount of NO2 in the exhaust gas stream, the flow rate of urea can be expressed according to the following equation: m˙NOx0.5∗(MWureaMWNOx) where MW Harnstoff the molecular weight of urea and MW NOx the molecular weight of NO x in the exhaust gas stream. If the amount of NO in the exhaust gas stream is less than or equal to the amount of NO2 in the exhaust gas stream, the flow rate of urea can be expressed according to the following equation: m˙NOx0.5∗(MWureaMWNOx)2(a+1)3

[0093] In some implementations, the inverse reducing agent hydrolysis module 334 can communicate with the reducing agent modifier module 390 in data-receiving communication to receive a reducing agent modifier request 342 (see Fig. 15) As described in more detail below, the reducing agent modifier request 342 contains instructions to increase or decrease the reducing agent injection request 332 based on whether one or more reducing agent limiting conditions are present. Accordingly, the inverse reducing agent hydrolysis module 334 can be actuated to modify the reducing agent injection request 332 according to the reducing agent modifier request 342. Ammonia storage module

[0094] With reference to Fig. 10. The NH3 storage module 350 can be activated to determine an ammonia storage modifier or storage compensation instruction 352. Generally, the ammonia storage modifier 352 contains information regarding the state of the ammonia storage on the SCR catalyst 152. In particular, the ammonia storage modifier 352 contains instructions on whether the ammonia entering the SCR catalyst 152 should be increased or decreased, e.g., whether the ammonia supplement request should be increased or decreased. The ammonia setpoint module 310 can communicate with the NH3 storage module 350 in data-receiving communication mode to receive the ammonia storage modifier 352 as an input value. Based on the ammonia storage modifier 352, the ammonia setpoint module 310 can be actuated to adjust the ammonia supplementary request 326, e.g.to increase or decrease in order to compensate for modulations in the ammonia storage concentration on the SCR catalyst 152 and to maintain a sufficient amount of stored NH3 on the SCR catalyst for temporary operations of the engine 11.

[0095] As discussed above, the performance of the SCR system 150 is determined by the conversion efficiency of NO. x The exhaust gas flow and the amount of ammonia emitted from the tailpipe are defined as both steady-state and transient duty cycles. During transient duty cycles, the response of conventional control systems, which only monitor the NO x -Monitor the concentration at the tailpipe outlet, taking into account the dynamics of the reducing agent dosing system and the cross-sensitivity of NO. x-Sensors to NH3 and other factors are limited. Accordingly, conventional control systems may exhibit unstable feedback controls during unsteady duty cycles. To improve the response and feedback controls during unsteady duty cycles, the SCR System 150 utilizes the NH3 stored on the SCR catalyst to counteract unsteady NO. x -to manage peaks that may occur during transient operation or transient cycles of the engine 11. Furthermore, the NH3 stored on the SCR catalyst 152 can be used to reduce NO xto reduce the amount of reducing agent required when engine system operating conditions, such as low SCR catalyst bed temperatures, necessitate a reduction or elimination of the reducing agent dosage. The NH3 storage module 350 is configured to monitor and control the amount of ammonia stored on the SCR catalyst 152, ensuring that a sufficient amount of stored NH3 is maintained on the SCR catalyst to suppress unsteady NO emissions. x -to take into account variations and low catalyst bed temperatures and to reduce NH3 slip.

[0096] The NH3 storage module 350 contains a current NH3 storage concentration module 354 and a target NH3 storage concentration module 356. The modules 354 and 356 process one or more inputs received from the NH3 storage module 350, as explained in more detail below. Current Ammonia Storage Concentration Module

[0097] With reference to Fig. 11 The current NH3 storage concentration module 354 can communicate with multiple sensors in data-receiving communication to receive data acquired by the sensors. In the illustrated embodiment, the multiple sensors include at least the SCR catalyst bed temperature sensor 124C, the NH3 sensors 166A-C, and the NO x -Sensors 164A-D. The current NH3 storage concentration module 354 can also provide a value for the AMOX-NH3 conversion capability 382 and a corrected tailpipe NO. x -Value 399 received, as described in more detail below.

[0098] The current NH3 storage concentration module 354 also includes an SCR catalyst inlet exhaust gas properties module 358, an NH3 flow module 364, and an SCR catalyst inlet NO2 / NO x-ratio module 366, an SCR catalyst degradation factor module 368, an SCR catalyst NH3 slip module 369, and an NH3 desorption module 375. Based on the input received from sensors 124C, 166A-C, 164A-D, the AMOX-NH3 conversion capability 382 (if an AMOX catalyst is used), the tailpipe NO x-Feedback value 399 and the operation of modules 358, 364, 366, 368, 369, 375, the current NH3 storage concentration module 354 can be operated to determine the current NH3 storage concentration 370 (e.g., an estimate of the current amount of NH3 stored on the SCR catalyst 152, at least partially based on the SCR catalyst bed temperature), the current NH3 slip 372 (e.g., an estimate of the current amount of NH3 exiting the SCR catalyst), and the maximum NH3 storage capacity 374 (e.g., an estimate of the maximum amount of NH3 that can be stored on the SCR catalyst, based on current conditions). The proportion of the available storage on the SCR catalyst that is filled can be determined by dividing the current NH3 storage concentration 370 by the largest NH3 storage capacity 374.

[0099] The SCR catalyst inlet exhaust gas properties module 358 is similar to the SCR catalyst inlet exhaust gas properties module 316 of the ammonia setpoint module 310. For example, the exhaust gas properties module 358 can be operated to determine various properties of the exhaust gas, such as the temperature and the flow rate of the exhaust gas.

[0100] The NH3 flow module 364 can be activated to determine the rate at which NH3 flows into the SCR catalyst 152. The NH3 flow module 364 can also process data regarding the amount of NH3 present at the tailpipe outlet after detection by the NH3 sensor 166C. The NH3 sensor 166C at the tailpipe outlet supports the measurement and control of tailpipe NH3 slip by providing tailpipe NH3 slip information to various modules of the controller 130. In some cases, the modules, e.g., the target NH3 storage concentration module 356 and the reducing agent modifier module 390, adjust the urea dosing rate and the ammonia storage targets, at least partially, based on the tailpipe NH3 slip information received from the NH3 sensor.

[0101] The SCR catalyst inlet NO2 / NO x The ratio module 366 is similar to the SCR catalyst inlet NO2 / NO. x-ratio module 314 of the ammonia setpoint module 310. For example, the SCR catalyst inlet NO2 / NO x -ratio-module 366 is activated, the NO2 / NO x -Ratio of exhaust gas in the exhaust gas stream according to equation 1.

[0102] The SCR catalyst degradation factor module 368 can be actuated to determine a degradation factor or a state of the SCR catalyst 152 in a manner that is the same or similar to the NO x -Reduction efficiency module 312 of the above-described ammonia target module 310 is.

[0103] According to one embodiment, the current NH3 storage concentration module 354 determines the estimated current NH3 storage concentration 370 at least partially by utilizing the current state of the SCR catalyst bed, the size and properties of the SCR catalyst bed, and the ammonia flow entering the SCR catalyst. With reference to Fig. 12 and according to one embodiment, the NH3 storage concentration module 354 uses the schematic flow diagram 500 to determine the current NH3 storage concentration 370 on the SCR catalyst 152. The reducing agent setpoint module 330 can be actuated at 510 to determine the reducing agent injection request 332, e.g., the urea dosing rate. Alternatively, the current NH3 storage concentration module 354 can communicate with the reduction feed mechanism 190 in data-receiving communication to receive the current reducing agent dosing rate 383. The SCR catalyst bed temperature sensor 124C detects, or a bed temperature module estimates, the temperature of the SCR catalyst bed at 520.

[0104] At least partially based on the temperature of the SCR catalyst bed, as determined at 520, the maximum NH3 storage capacity 374 at 530 is generated by the current NH3 storage concentration module 354. The maximum NH3 storage capacity 374 depends on the temperature of the SCR catalyst bed and can be determined by comparing the SCR catalyst bed temperature with a pre-calibrated lookup table. The urea dosing rate, corresponding to the ammonia flow entering the SCR catalyst 152, and the SCR catalyst bed temperature are used to determine an NH3 replenishment or adsorption time constant, and the SCR catalyst bed temperature and the NO x The flow rates are used to determine an NH3 removal or desorption time constant. The time constants can be retrieved from the respective lookup tables 540, 550, stored, for example, on the current NH3 storage concentration module 354.

[0105] The SCR catalyst mode is determined at 560. Based on whether the SCR catalyst 152 is in an NH3 refill mode or an NH3 removal mode, the corresponding time constant (τ) is used to calculate the current NH3 storage concentration (NH3Storage) at 570 according to the following first-order dynamic equation: NH3Storage=NH3StorageMAX(1τs+1) where NH3Storage MAXThe maximum NH3 storage capacity 374 of the SCR catalyst 152 and s is the complex variable used for the Laplace transforms. In other words, if it is determined at 560 that more ammonia should be stored on the SCR catalyst 152, the NH3 adsorption time constant determined at 540 is used in Equation 16 to determine the current NH3 storage concentration 370. Alternatively, if it is determined at 560 that ammonia should be removed from the SCR catalyst 152, the NH3 desorption time constant determined at 550 is used in Equation 16 to determine the current NH3 storage concentration 370. Accordingly, the current NH3 storage concentration 370 is based at least partially on the ammonia flux, the catalyst temperature, and the catalyst degradation.

[0106] In at least one embodiment, the storage mode, e.g., replenishment or disposal mode, of the SCR catalyst 152 is determined by the NH3 storage module 350 by comparing the maximum NH3 storage capacity 374 with the current NH3 storage concentration 370. If the maximum NH3 storage capacity 374 is less than the current NH3 storage concentration 370, then the SCR catalyst 152 is in desorption mode. Similarly, if the maximum NH3 storage capacity 374 is greater than the current NH3 storage concentration 370, then the SCR catalyst 152 is in adsorption mode.

[0107] The lookup tables used in references 540 and 550 contain a list of adsorption and desorption time constants corresponding to various possible urea dosing rates and SCR catalyst bed temperatures. In certain implementations, the adsorption time constants can be calibrated via steady-state testing. For example, the engine 11 can operate in specific steady-state modes such that the temperature of the SCR catalyst bed reaches and is maintained at a specific temperature corresponding to each mode. Before reaching each mode, the SCR catalyst 152 is clean, so that the catalyst bed contains no stored ammonia, i.e., the NO coming from the engine. x The amount is equal to the NO coming from the SCR catalyst. x-Quantity. For each respective mode, the reducing agent setpoint module 330 can be activated to communicate with the reducing agent supply mechanism 190, in order to achieve a 100% conversion of NO. x The required amount of reducing agent is injected. The amount of reducing agent can vary for different stoichiometric reaction rates, for example, in the range between approximately 0.5 and approximately 2.0. The time between the initial reducing agent injection and the ammonia slip from the SCR catalyst 152 is determined for each mode at each stoichiometric reaction injection rate and used to calibrate the adsorption time constants in the NH3 replenishment time constant table.

[0108] The desorption time constants in the NH3 removal time constant table can be calibrated during the same test used to calibrate the adsorption time constants. For example, after the onset of NH3 release from the SCR catalyst 152 as described above, the NH3 slip and the NO leaving the SCR catalyst are measured. x monitored until they stabilize or become constant. After the NH3 slip and the SCR catalyst outlet NO x If the values ​​are stable, the urea dosing is interrupted and the time interval between the interruption of the urea dosing and the SCR catalyst outlet NO is recorded. x to match the engine exhaust NO x is determined for each mode at each stoichiometric reaction dosing rate.

[0109] If desired, the adsorption and desorption time constants can be further calibrated to compensate for unsteady operation of the motor 11. For example, Fourier transform infrared (FTIR) measurements of ammonia slip values ​​and the time between the start of an unsteady FTP cycle and slip from the SCR catalyst can be used to fine-tune the adsorption and desorption time constants. In particular, the time constants can be adjusted based on a least squares approach, which can provide the best first-order model to fit the unsteady data.

[0110] The target NH3 storage concentration module 356 can be activated to determine a target NH3 storage concentration, at least partially, based on the maximum NH3 storage capacity 374 determined by the current NH3 storage concentration module 354. In general, the target NH3 storage concentration module 356 determines the target NH3 storage concentration by multiplying the maximum NH3 storage capacity 374 by an ammonia storage capacity fraction. The ammonia storage concentration fraction can be any of several different fractions, such as 50%, 75%, 90%, or 100%. The ammonia storage concentration fraction is determined, at least partially, based on the SCR catalyst degradation factor and the user-defined maximum permissible ammonia slip.

[0111] After the current NH3 storage capacity 370 and the target NH3 storage concentration have been determined, the NH3 storage module 350 uses the current NH3 storage concentration 370 as feedback and compares the current NH3 storage concentration with the target NH3 storage concentration. If the current NH3 storage concentration is below the target NH3 storage concentration, the ammonia storage modifier 352 is set to a positive value. If the current NH3 storage concentration 370 is above the target NH3 storage concentration, the ammonia storage modifier 352 is set to a negative value. The positive and negative values ​​can vary depending on how much lower or higher the current NH3 storage concentration 370 is compared to the target NH3 storage concentration. The ammonia storage modifier 352 is communicated to the ammonia target module 310 (see Fig. 5) An ammonia storage modifier 352 with a positive value indicates to the ammonia setpoint module 310 that the ammonia supplementary requirement 326 should be increased accordingly. Conversely, an ammonia storage modifier 352 with a negative value indicates to the ammonia setpoint module 310 that the ammonia supplementary requirement 326 should be decreased accordingly.

[0112] The extent of NH3 storage on the catalyst 152 can be controlled or regulated by controlling or regulating any one of the various inputs to the SCR system 150. For example, with reference to Fig. 12 The extent of ammonia storage on the SCR catalyst 152 depends on the following separately controllable factors: the urea dosing rate, the SCR catalyst bed temperature, and the maximum SCR catalyst capacity. Accordingly, the controller 130 can be actuated to selectively or cooperatively control the current NH3 storage concentration on the SCR catalyst 152.

[0113] The ammonia storage modifier 352 can also be adjusted according to the current NH3 storage slip 372, the presence or absence of an AMOX catalyst such as the AMOX catalyst 160 and, if an AMOX catalyst is used, the conversion capability 382 of the AMOX catalyst.

[0114] According to one embodiment, the SCR catalyst ammonia slip module 369 determines the estimated current NH3 slip 372 from the SCR catalyst 152 by at least partially determining the ammonia and NO xThe flow entering the catalyst, the size and properties of the SCR catalyst bed, and the NO to NO2 ratio are used. With reference to Fig. 13 and according to one embodiment, the ammonia slip module 369 uses the schematic flow diagram 600 to determine the current NH3 slip 372 from the SCR catalyst 152. The NO x The amount at the inlet of the SCR catalyst 152 is determined at 610, and the NO x The amount of NO at the SCR catalyst outlet is determined at 614. x -Inlet quantity can be determined by the NO x -Sensor 164A and / or 164E are detected, and the NO x -Outlet quantity can be determined by the NO x -Sensor 164C or the NO x -Sensor 164D can be detected. In certain implementations, the NO x -Concentrations within the SCR catalyst after detection by the NO x-Sensor 164B of the SCR catalyst ammonia slip module 369 can be used to obtain an even more accurate estimate of the ammonia escaping from the SCR catalyst 152.

[0115] The NO x The sensor 164B, when embedded in the SCR catalyst 152, offers several advantages over state-of-the-art systems. For example, the placement of the NO improves x -Sensors 164B in the SCR catalyst 152 monitor the stored ammonia on the catalyst by reducing the signal-to-noise ratio of the NO x -Sensors. The NO x Sensor 164B can be used with other NOs x -Sensors are used in the exhaust aftertreatment system 100, for example the NO xSensors 164C, 164E are used to quantify the spatial distribution of stored ammonia on the SCR catalyst 152. In certain embodiments, the SCR catalyst 152 comprises two spaced-apart ceramic catalyst elements or beds extending parallel to each other. The embedded NO x Sensor 164B can be positioned between the beds, e.g., within the space between the beds, at any point along the length of the SCR catalyst 152. In certain cases, the embedded NO x -Sensor 164B is positioned between the beds at an approximately central point between the ends of the SCR catalyst 152.

[0116] To account for any potential degradation of sensor 164D, the NO output can be adjusted. x -Sensors 164D as described above in relation to the corrected tailpipe NO xModule 362 is corrected. The ratio of NO to NO2 in the exhaust gas stream at the inlet of the SCR catalyst 152 is determined at 612, and the ratio of NO to NO2 in the exhaust gas stream at the outlet of the SCR catalyst is determined at 616. In some implementations, the SCR catalyst NO2 / NO x -ratio module 366 is operated to determine the NO to NO2 ratios at the inlet and outlet of the SCR catalyst 152.

[0117] At 620, the amount of ammonia consumed in the SCR catalyst 152 is calculated based on the net loss, e.g., the conversion, of NO and NO2 from the exhaust gas stream. In some implementations, the calculation is performed by the current NH3 storage concentration module 354. At least partially based on the NH3 flow rate into the SCR catalyst 152 determined at 630 and the amount of ammonia consumed in the SCR catalyst 152, the excess NH3 in the SCR catalyst is determined at 640. As described above, the amount of NH3 flowing into the SCR catalyst 152 can be determined using the flow diagram 400. Fig. 10 will be determined.

[0118] Furthermore, at 660, the amount of ammonia desorbed from the bed of the SCR catalyst 152 is determined, at least partially, based on the current NH3 storage concentration 370 determined at 650, the exhaust gas flow rate into and through the SCR catalyst 152 determined at 652, and the temperature of the SCR catalyst bed determined at 653. Generally, ammonia desorption occurs when there is a specific increase in the temperature of the SCR catalyst bed. The extent of the temperature increase required to cause ammonia desorption depends, at least partially, on the condition and type of the SCR catalyst used. As in Fig. As shown in Figure 11, the current NH3 storage concentration module 354 can contain the desorbed NH3 module 375, which can be actuated to estimate the amount of ammonia desorbed from the bed of the SCR catalyst 152. In certain implementations, the NH3 storage concentration module 354 estimates the amount of ammonia desorbed from the bed of the SCR catalyst based on the NO available for a reduction reaction on the SCR catalyst surface. x -Excess flow: the amount of ammonia desorbed from the SCR catalyst bed.

[0119] At least partially based on the excess NH3 quantity in the SCR catalyst 152, the quantity of NH3 desorbed from the SCR catalyst bed, and the quantity of NH3 stored on the SCR catalyst relative to the catalyst's largest NH3 storage capacity 374 (i.e., the portion of the SCR catalyst occupied by the stored ammonia), the quantity of NH3 escaping from the SCR catalyst is estimated at 680. The quantity of NH3 escaping from the SCR catalyst 152 is equal to the sum of the excess NH3 quantity determined at 640 and the desorbed NH3 quantity determined at 660. The proportion of the SCR catalyst occupied by stored ammonia is determined at 670 by dividing the NH3 stored on the catalyst after determination at 650 by the maximum NH3 storage capacity determined, for example, at 530 of the flowchart 500. If the total amount of NH3 stored on the SCR catalyst 152 is greater than the maximum NH3 storage capacity 374, i.e.,If the ammonia storage fraction determined at 670 is greater than 1, then ammonia slip from the catalyst generally occurs, and the extent of the slip is determined at 680. If the total amount of NH3 in the SCR catalyst is below the maximum NH3 storage capacity 374, i.e., the ammonia storage fraction is less than one, then no ammonia slip occurs, and the extent of the ammonia slip is not calculated at 680. In other words, the model used to calculate the ammonia slip at 680 only becomes active when the SCR catalyst 152 is full of ammonia or when the SCR catalyst bed temperature and the rate of increase of the SCR catalyst bed temperatures exceed predetermined thresholds.

[0120] The extent of NH3 slip from the catalyst 152 can be controlled or regulated by controlling or regulating any one of the various inputs to the SCR system 150. For example, with reference to Fig. 13 The extent of ammonia slip from the SCR catalyst 152 depends on the following separately controllable or adjustable factors: the amount of NH3 flowing into the SCR catalyst as determined at 630; the exhaust gas flow rate as determined at 652; and the current NH3 storage concentration as determined using the flow diagram 500. Accordingly, the controller 130 can be actuated to selectively or cooperatively control or regulate the NH3 slip from the SCR catalyst.

[0121] If the current NH3 storage slip 372 is relatively high, for example, if the temperature of the SCR catalyst bed exceeds a predetermined level, then the NH3 storage module can be activated to decrease the ammonia storage modifier 352. Conversely, if the current NH3 storage slip 372 is relatively low, the NH3 storage module can then be activated to increase or maintain the ammonia storage modifier 352. AMOX ammonia conversion module

[0122] According to a Fig. In the embodiment shown in Figure 14, the AMOX-NH3 conversion module 380 determines an AMOX-NH3 conversion capability or efficiency 382, ​​an exhaust pipe NH3 slip 384, and a thermal AMOX catalyst mass 385. In general, the NH3 conversion capability 382 represents an estimate of the ability of the AMOX catalyst 160 to convert NH3 to N2 and other less hazardous or less harmful components. The exhaust pipe NH3 slip 384 represents an estimate of the amount of NH3 exiting the AMOX catalyst 160. As described in more detail below, the thermal AMOX mass 385 is a measure of the ability of the AMOX catalyst to conduct and store heat.

[0123] The AMOX-NH3 conversion module 380 receives input regarding the exhaust gas flow rate 700 entering the AMOX catalyst 160 and the amount of NH3 entering the AMOX catalyst. In some implementations, the exhaust gas flow rate 700 is determined by the SCR catalyst inlet exhaust gas properties module 358 of the current NH3 storage concentration module 354 (see Fig. 11) or another similar module. The amount of NH3 entering the AMOX catalyst 160 can be represented by an NH3 input 712 and / or the current NH3 slip 372. In particular, in some implementations, the AMOX NH3 conversion module 380 can communicate with the current NH3 storage concentration module 354 in data-receiving communication to receive the current NH3 slip 372. In these implementations, the amount of NH3 entering the AMOX catalyst 160 can be set to the current NH3 slip 372. In some implementations, the control system 150 can include an NH3 sensor between the SCR catalyst 152 and the AMOX catalyst 160. In these implementations, the amount of NH3 entering the AMOX catalyst 160 can be set to the output of the NH3 sensor.Alternatively, in certain cases, the amount of NH3 entering the AMOX catalyst 160 can be set to a combination of the current NH3 slip 372 and the output of the NH3 sensor, such as an average of the current NH3 slip 372 and the output of the NH3 sensor. The AMOX NH3 conversion module 380 can also be used in data-receiving communication with various other sensors, such as temperature sensors 124D, 124E, and NO. x -Sensor 164C communicate.

[0124] The AMOX-NH3 conversion module 380 contains several modules, including an AMOX catalyst bed temperature module 386 and an NO2 / NO x -ratio module 387, an AMOX catalyst degradation module 388 and an exhaust pipe NH3 slip setpoint module 389.

[0125] The AMOX catalyst bed temperature module 386 can be operated to estimate the temperature of the AMOX catalyst bed. In one implementation, the AMOX catalyst bed temperature module 386 uses the input from temperature sensors 124D and 124E to determine the difference between the exhaust gas temperature at the inlet of the AMOX catalyst 160 and the exhaust gas temperature at the outlet of the AMOX catalyst. Based at least partially on the temperature differential and the mass flow characteristics of the exhaust gas stream, the AMOX catalyst bed temperature module 386 calculates the temperature of the AMOX catalyst bed. Alternatively or additionally to estimating the AMOX catalyst bed temperature as described above, the SCR system 150 can include a temperature sensor (not shown) coupled to the AMOX catalyst 160.The AMOX catalyst bed temperature module 386 can use the output of the AMOX catalyst temperature sensor to determine the temperature of the AMOX catalyst bed.

[0126] Similar to the SCR catalyst NO2 / NO x The ratio module 366 of the current NH3 storage concentration module 354 can determine the NO2 / NO x The ratio module 387 of the AMOX-NH3 conversion module 380 is actuated, the ratio of NO2 to NO x to be determined according to equation 1 above, where NO2 is the amount of nitrogen dioxide at the inlet of the AMOX catalyst 160 and NO is the amount of nitrogen oxide at the inlet of the AMOX catalyst, as determined by the NO x -Sensor 164C determined.

[0127] Analogous to the SCR catalyst degradation factor module 368 of the current NH3 storage concentration module 354, the AMOX catalyst degradation module 388 can be activated to determine an AMOX catalyst degradation factor that indicates the condition of the AMOX catalyst. In certain implementations, the catalyst degradation factor is determined by an algorithm that compares the conversion efficiency of the "aged" AMOX catalyst under predetermined engine operating conditions and urea dosing rates with the conversion efficiency of a "fresh" AMOX catalyst under the same predetermined conditions and dosing rates.

[0128] The tailpipe NH3 slip setpoint module 389 can be activated to determine a tailpipe NH3 slip setpoint, i.e., the desired amount of NH3 permitted to escape from the AMOX catalyst 160. The tailpipe NH3 slip setpoint is based at least partially on a desired average level of NH3 slip from the AMOX catalyst and / or a desired maximum level of NH3 slip from the AMOX catalyst. In some cases, both the desired average level of NH3 slip from the AMOX catalyst and the desired maximum level of NH3 slip from the AMOX catalyst are used to ensure that the actual tailpipe slip levels remain below a human-detectable threshold. Furthermore, the tailpipe NH3 slip setpoint can be based on other factors such as current emission standards and customer-specific requirements.

[0129] At least partially based on at least the exhaust gas flow rate, NO x, and / or ammonia entering the AMOX catalyst 160, the temperature of the AMOX catalyst bed, the NO2 / NO ratio x Based on the AMOX catalyst inlet, the catalyst degradation factor, and / or the tailpipe NH3 slip target, the AMOX-NH3 conversion module 380 estimates the AMOX-NH3 conversion capability 382, ​​the tailpipe NH3 slip 384, and the thermal AMOX catalyst mass 385. For example, in some implementations, the AMOX-NH3 conversion capability 382 and the tailpipe NH3 slip 384 depend on the NO entering the AMOX catalyst. xThe thermal mass of the AMOX catalyst depends on the amount of NH3, the temperature of the AMOX catalyst, and its space velocity. Furthermore, in some cases, the thermal mass of the AMOX catalyst 385 is based at least partially on the geometric dimensions and material properties of the AMOX catalyst, such as its thermal conductivity and volumetric heat capacity. In some cases, the AMOX-NH3 conversion capability 382, ​​the tailpipe NH3 slip 384, and the thermal mass of the AMOX catalyst 385 can be estimated by accessing a multidimensional, pre-calibrated lookup table stored on the controller 130.

[0130] The higher the AMOX catalyst conversion capacity 382, ​​the greater the tolerance of the SCR system 150 in general to NH3 escaping from the SCR catalyst 152. If the AMOX catalyst conversion capacity 382 is relatively high, more NH3 can be allowed to escape from the SCR catalyst 152. However, if more NH3 escapes from the SCR catalyst 152, more NH3 storage sites on the surface of the SCR catalyst 152 may be vacant, necessitating an increase in the ammonia storage requirement 326. In such a case, the NH3 storage module 350 can increase the ammonia storage modifier 352, which in turn can increase the ammonia storage requirement 326. If, in contrast, the AMOX catalyst conversion capability 382 is relatively low, less NH3 slip from the SCR catalyst 152 is tolerated, resulting in less NH3 being removed from the storage on the SCR catalyst.If more NH3 escapes from the SCR catalyst 152 and the AMOX catalyst conversion capability 382 is relatively low, the tailpipe NH3 slip can increase accordingly. Therefore, in these cases, the NH3 storage module 350 can reduce or maintain the ammonia storage modifier 352 to reduce or maintain the ammonia supplement requirement 326, and / or the AMOX NH3 conversion module 380 can modulate the efficiency of the AMOX catalyst 160 so that the tailpipe NH3 slip is controlled or regulated.

[0131] In some implementations, the value of the AMOX thermal catalyst mass (385) depends on the material properties of the AMOX catalyst bed, such as its thermal conductivity and volumetric heat capacity. Generally, the thermal mass (385) is a measure of the AMOX catalyst's ability to conduct and store heat. The AMOX-NH3 conversion module (380) can communicate the value of the AMOX thermal catalyst mass (385) to the NH3 storage module (350), which can then use this value in determining the ammonia storage modifier (352).

[0132] As described above, the AMOX-NH3 conversion capability and the thermal AMOX catalyst mass 385 are communicated to and processed by other modules of the controller 130. For example, the AMOX-NH3 conversion capability 382 and the thermal AMOX catalyst mass 385 are received by the NH3 storage module 350 and used to determine the ammonia storage modifier 352 (see Fig. 10). Furthermore, the AMOX-NH3 conversion capacity 382 is determined by the corrected tailpipe NOₓ x Module 399 is used to determine the tailpipe NO. x -to determine feedback value 399 (see Fig. 16).

[0133] The tailpipe NH3 slip 384 determined by the AMOX-embedded model NH3 conversion module 380 can be communicated to other modules of the controller 130. For example, the determined tailpipe NH3 slip 384 can be communicated to the reducing agent modifier module 390 (see Fig. 15) and the corrected tailpipe NO x-Module 397 (see Fig. 16) communicated to replace or supplement the tailpipe NH3 slip measurement input communicated by the NH3 sensor 166C. For example, in certain cases, the tailpipe NH3 input value to modules 390, 397 can be an average of the specified tailpipe NH3 slip 384 and the tailpipe NH3 slip measurement from sensor 166C to provide a more accurate indication of the actual amount of NH3 escaping from the tailpipe. Reducing agent modifier module

[0134] With reference to Fig. 15 The reducing agent modifier module 390 can be actuated, at least partially on the basis of which a reducing agent modifier requirement 342 is determined as to whether any of the various reducing agent limiting conditions have been met. The reducing agent modifier module 390 includes a reducing agent modifier conditions module 394 and an SCR catalyst inlet exhaust gas properties module 395. In general, the reducing agent modifier module 390 can be actuated either to reduce the reducing agent dosage, to prevent reducing agent dosage, or to leave the reducing agent dosage unchanged when certain predetermined conditions of the exhaust aftertreatment system 100 are met.

[0135] The reducing agent modifier condition module 394 can be actuated to monitor the operating conditions of the engine system 10 and to determine whether one or more reducing agent limiting conditions are met. In some embodiments, the reducing agent limiting conditions include, among others, an exhaust gas temperature limit, an ammonia slip reducing agent rate limit, and an SCR catalyst bed temperature limit.

[0136] Reducing agent dosing at high exhaust gas temperatures can cause the formation of cyanuric acid and polymers (e.g., melamine) on the injector and exhaust pipe walls, which can lead to reduced performance and system damage. For example, melamine formation can clog the nozzle. To prevent cyanuric acid formation, the reducing agent modifier module 390, together with the reducing agent modifier condition module 394, monitors the exhaust gas temperature and prevents reducing agent dosing, e.g., via instructions in the reducing agent modifier request 342, if the exhaust gas temperature exceeds a predetermined exhaust gas temperature limit. The current exhaust gas temperature can be detected by at least one of the temperature sensors, e.g., exhaust gas temperature sensor 124C, and / or predicted by an SCR catalyst inlet exhaust gas properties module 395, similar to module 358.

[0137] High SCR catalyst storage capacities and SCR catalyst bed temperature ramps can cause ammonia to escape from the SCR catalyst 152. To reduce ammonia slip in these situations, the reducing agent modifier module 390 monitors the current NH3 storage concentration 370 and the modulations of the SCR catalyst bed temperature as detected by the temperature sensor 124D (or predicted by an SCR catalyst bed temperature module, as described above). If the current NH3 storage concentration 370 exceeds a predetermined NH3 storage concentration associated with NH3 slip, or if the modulation of the SCR catalyst bed temperature exceeds a predetermined SCR catalyst bed temperature change, then the reducing agent modifier module reduces the reducing agent dosing rate, e.g.via instructions in the reducing agent modifier request, so that NH3 slip from the SCR catalyst 152 is controlled or regulated.

[0138] The reducing agent modifier module 390 can also be activated to prevent reducing agent dosing in the event that one or more specific components of the SCR system 150 malfunction or are otherwise not operational. Corrected tailpipe NO z -Module

[0139] With reference to Fig. 16 can the corrected tailpipe NO x -Module 397 of controller 130 is activated, the corrected tailpipe NO x -Value 399 to be determined. The corrected tailpipe NO x Module 397 can communicate with the tailpipe NO in data-receiving mode. x -Sensor 164D and the tailpipe NH3 sensor 166C communicate. The corrected tailpipe NO xModule 397 can also communicate in data-receiving communication with the current NH3 storage concentration module 354 to receive the estimated current NH3 slip 372 or the estimated amount of NH3 exiting the SCR catalyst 152. Furthermore, the corrected tailpipe NO x Module 397 communicates in data-receiving communication with the AMOX-NH3 conversion module 380 to receive the AMOX-NH3 conversion capability 382. The corrected tailpipe NO x Module 397 also contains a sensor degradation module 398, which can be actuated to create an end pipe NO. x -Sensor degradation factor to be determined at least partially based on the type of sensor, the age of the sensor and the operating conditions of the engine system 10. In some cases, the tailpipe NO x -Sensor degradation factor determined by an algorithm that measures the NO x Sensor measurements under predetermined operating conditions with known NO x-values ​​are compared. The degradation factor indicates the extent, e.g., a percentage, by which the measured NO degrades. x The sensor value should be adjusted to account for the degradation of NO. x -Sensors and with the measurements of degraded NO x -Sensor-associated inaccuracies must be taken into account. In some implementations, the corrected tailpipe NO is x -Value approximately 10% higher than the measured tailpipe NOₓ x -Value.

[0140] The corrected tailpipe NO x Module 397 processes the recorded tailpipe NO x -Quantity, the detected tailpipe NH3 quantity, the estimated NH3 slip 372, the NO x -Sensor degradation factor and the AMOX conversion capability 382 to determine the corrected tailpipe NO x -value 399 to be determined. The corrected tailpipe NO x A value of 399 can be determined from the tailpipe NO. x Sensor 164D detected recorded NO x-Quantity in the calculation of the reducing agent modifier requirement 342 by the reducing agent modifier module 390 by a more precise specification of the NO leaving the tailpipe x -Quantity and a more precise reducing agent modifier requirement can be replaced. Furthermore, the corrected tailpipe NO can x The value 399 is communicated to the current NH3 storage concentration module 354 and processed by it. On-board diagnostic system

[0141] In some embodiments, the SCR system 150 is coupled to an on-board diagnostics (OBD) system with an OBD interface 900 (see Fig. 2) In particular, the SCR system controller 130 is electronically coupled to the OBD interface 900 and sends a diagnostic data packet 920 (see Fig. 3) Regarding the various components of the SCR system 100, interface 900 is used. In some implementations, interface 900 includes an indicator element, such as a warning light. Based on diagnostic data packet 920, if, for example, diagnostic data packet 920 communicates that a component is malfunctioning, the indicator element is activated to warn a user about the detected malfunctioning component. In some implementations, diagnostic data packet 920 is communicated to interface 900 when requested by an operator. For example, interface 900 may be a connector to which a sampling tool is coupled. The diagnostic data packet 920, or associated diagnostic data, is then uploaded to the sampling tool for further evaluation.

[0142] With reference to Fig. 2. The controller 130 can contain an OBD module 910 configured to collect diagnostic data regarding the SCR system 150 and to generate a diagnostic data package 920. Generally, the OBD module 910 receives data from modules 300, 310, 330, 344, 350, 380, 390, and 397 regarding the operation of the SCR catalyst 152 and the reducing agent supply system 151. Specifically, based on the data received from the modules, the OBD module 910 determines whether the SCR catalyst 152 and the reducing agent supply system 151 are operating with proper NOₓ. x -Conversion capacity or capability. The OBD module 910 is configured to detect a malfunction of the SCR system when the NO x -Conversion capacity of the system 150 is such that the tailpipe NO x -Emissions exceed the regulated upper limit by a specific regulated factor, such as 1.75 times the regulated upper limit.

[0143] For example, if in one embodiment the largest NO x -Conversion efficiency of the SCR catalyst 152 after determination by NO x -Reduction efficiency module 312 is insufficient to reduce the NO escaping from the tailpipe x To limit the quantity to an amount below the regulated upper limit multiplied by the regulated factor, the OBD module 910 generates a diagnostic data package 920 indicating a malfunction of the SCR system. As another example: if the reducing agent supply mechanism 190 is sufficiently degraded such that the maximum amount of reducing agent that can be injected by the supply mechanism is insufficient for the SCR catalyst 152 to reduce the NO xIf the amount of NO can be reduced to a quantity below the regulated upper limit multiplied by the regulated factor, the OBD module 910 also generates a diagnostic data package 920 indicating a malfunction of the SCR system. Although only the degradation of the SCR catalyst 152 and the feed mechanism 190 are specifically described as a cause for indicating a malfunction of the SCR system, in other embodiments the OBD module 910 can generate a diagnostic data package 920 indicating a malfunction of the SCR system if the degradation or malfunction of any other components of the engine system 10 contributes to the inability of the SCR system 150 to reduce the NO escaping from the tailpipe. x-To limit the quantity to an amount below the regulated upper limit multiplied by the regulated factor. Other components of the engine system 10 may include the air handling system, the fuel supply system, the EGR system, the oxidation catalyst, the PM filter, and the AMOX catalyst. Exemplary method for reducing NO x -Emissions

[0144] With reference to Fig. 17 and according to a representative embodiment, a method 800 for reducing NO is described x Emissions using an ammonia storage system on an SCR catalyst are shown. The procedure 800 begins at 802 and includes determining 804 a NO x -Reduction requirement. In some implementations, determining 804 of a NO involves x -Reduction requirement: actuating the NO x -Reduction target module 300, the NO x-Reduction requirement 304 to be estimated. Procedure 800 also includes determining 806 an ammonia supplement requirement. In some implementations, determining 806 an ammonia supplement requirement involves actuating the ammonia setpoint module 310 to estimate the ammonia supplement requirement 326. Procedure 800 further includes determining 808 an ammonia storage modifier. In some implementations, determining 808 an ammonia storage modifier involves actuating the NH3 storage module 350 to estimate the ammonia storage modifier 352.

[0145] After an ammonia storage modifier has been determined, procedure 800 includes comparing 810 the ammonia storage modifier with a predetermined value, such as zero. If the ammonia storage modifier is greater or less than the predetermined value, then procedure 800 includes adjusting 812, such as by adding, to the ammonia supplement requirement determined in 808 by an amount corresponding to the amount of ammonia storage modifier. If the ammonia storage modifier is approximately equal to the predetermined value, then the ammonia supplement requirement determined in 808 is not adjusted. Procedure 800 includes determining 814 a reducing agent injection requirement 814 either based on the ammonia supplement requirement determined in 808 or the adjusted supplement requirement determined in 812.In some implementations, determining a reducing agent injection requirement (814) involves activating the reducing agent setpoint module (330) to calculate the reducing agent injection requirement (332). The procedure (800) may also involve determining an AMOX catalyst-NH3 conversion capability (815) (382) by activating the AMOX-NH3 conversion module (380).

[0146] Procedure 800 further includes determining 816 a reducing agent modifier. In some implementations, determining 816 a reducing agent modifier involves activating the reducing agent modifier module 390 to compute the reducing agent modifier requirement 342. After a reducing agent modifier has been determined, procedure 800 includes comparing 820 the reducing agent modifier with a predetermined value, such as zero. If the reducing agent modifier is greater or less than the predetermined value, procedure 800 then includes adjusting 822 the reducing agent injection requirement determined at 816 by an amount corresponding to the amount of reducing agent modifier. If the reducing agent modifier is approximately equal to the predetermined value, then the reducing agent injection requirement determined at 808 is not adjusted.The procedure involves injecting a quantity of reducing agent into the exhaust gas stream in accordance with the reducing agent injection requirement determined in 816 or 822.

[0147] The schematic flowcharts and schematic process diagrams described above are generally presented as logical flowcharts. As such, the sequence shown and the steps labeled indicate representative embodiments. Other steps and processes may be devised that are equivalent in function, logic, or effect to one or more steps or sections thereof of the processes depicted in the schematic diagrams. Furthermore, the format and symbols used are provided to explain the logical steps of the schematic diagrams and are not to be understood as limiting the scope of protection of the processes depicted by the diagrams. Although different types of arrows and line styles may have been used in the schematic diagrams, it is understood that they do not limit the scope of protection of the corresponding processes.In fact, some arrows or other connecting elements can be used simply to indicate the logical flow of a procedure. For example, an arrow might indicate a waiting or monitoring period of unspecified duration between enumerated steps of a depicted procedure. Furthermore, the order in which a particular procedure occurs may or may not strictly follow the sequence of the corresponding steps shown.

[0148] The present invention can be embodied in other specific forms without deviating from its underlying concept or essential characteristics. The described embodiments are to be regarded in every respect as illustrative only and not restrictive. The scope of protection of the invention is therefore specified by the appended claims instead of by the preceding description.

Claims

[1] Device for reducing NO x -Emissions in an engine exhaust stream of an engine system with a selective catalytic reduction system having an SCR catalyst (152) positioned downstream of a reducing agent injector (192), comprising: a NO x -Reduction setpoint module (300) that is configured to be NO x -reduction requirement to determine, whereby the NO x -Reduction requirement: an amount of NO to be reduced on the SCR catalyst (152) x in the exhaust gas stream, and a reducing agent module (330) configured to determine the amount of reducing agent to be added to the exhaust gas stream in order to reduce the NO x -To meet the reduction requirement, wherein an amount of reducing agent added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst (152), at least one reducing agent-to-ammonia conversion characteristic and a conversion capability of an AMOX catalyst (160) in exhaust gas receiving communication with the SCR catalyst (152). [2] Device according to claim 1, wherein the at least one ammonia storage characteristic comprises an estimated amount of ammonia stored on the SCR catalyst (152), an estimated amount of ammonia escaping from the SCR catalyst (152) and / or an estimated maximum ammonia storage capacity of the SCR catalyst (152). [3] Device according to claim 1, wherein the at least one reducing agent to ammonia conversion characteristic comprises the distance between the SCR catalyst (152) and the reducing agent injector (192), the conversion efficiency of the reducing agent to ammonia and / or the conversion efficiency of the reducing agent to components other than ammonia. [4] Device according to claim 1, wherein the conversion capability of the AMOX catalyst (160) is a function of the temperature of the AMOX catalyst (160), an AMOX catalyst degradation factor and / or an exhaust pipe ammonia slip setpoint. [5] Device according to claim 1, wherein the amount of reducing agent added to the exhaust gas stream is a function of a physical state of the SCR catalyst (152). [6] Device according to claim 5, wherein the physical state of the SCR catalyst (152) is determined by a degradation factor of the SCR catalyst (152) and / or a maximum NO x-Conversion efficiency of the SCR catalyst (152) is shown. [7] Device according to claim 1, further comprising an on-board diagnostic module (910) configured to determine whether a maximum NO x -Reduction efficiency of the SCR catalyst (152) is below a predetermined threshold. [8] Methods for reducing NO x -Emissions in an engine exhaust stream of an engine system flowing from an engine of the engine system to an exhaust pipe of the engine system, wherein the engine system has an SCR catalyst and a urea injector upstream of the SCR catalyst, the method comprising: Determining a NO x -reduction requirement, where the NO x -Reduction requirement: an amount of NO to be reduced on an SCR catalyst x in the exhaust stream Determining AMOX catalyst conversion capability, Determining an ammonia storage modifier, Determining an ammonia supplement requirement, wherein the ammonia supplement requirement comprises an amount of ammonia added to the exhaust gas stream to reduce the NO x -reduction requirement to be met, whereby the ammonia addition requirement depends at least partially on the AMOX catalyst conversion capability and the ammonia storage modifier, Determination of urea-to-ammonia and urea-to-isocyanic acid conversion factors, Determining a urea injection requirement at least partially based on the urea-to-ammonia and urea-to-isocyanic acid conversion factors, wherein the urea injection requirement includes an amount of urea added to the exhaust gas stream to meet the ammonia addition requirement, Determine whether at least one urea-limiting condition is met, and modifying the urea injection request if at least one urea-limiting condition is met, and Injecting urea into the exhaust gas stream according to the urea injection requirement. [9] Method according to claim 8, wherein the ammonia storage modifier is based at least partially on the estimated amount of ammonia stored on the SCR catalyst, the estimated amount of ammonia exiting the SCR catalyst and the estimated maximum ammonia storage capacity of the SCR catalyst. [10] Method according to claim 8, wherein the urea-to-ammonia and urea-to-isocyanic acid conversion factors are based at least partially on the distance between the SCR catalyst and the urea injector, a urea-to-ammonia conversion efficiency and a urea-to-isocyanic acid conversion efficiency. [11] Engine system comprising an internal combustion engine (11) that generates an exhaust stream, an SCR system (150) comprising an SCR catalyst (152) that reduces NO x -Emissions in the exhaust stream are reduced in the presence of ammonia, a reducing agent injector (192) that injects reducing agent into the exhaust gas stream upstream of the SCR catalyst (152), wherein the reducing agent provides the ammonia, and a controller (130) which has the following features: - a positive feedback component that is configured to deliver a reducing agent dosing rate corresponding to a desired level of NO x -reduction on the SCR catalyst (152) during steady-state operating conditions of the internal combustion engine (11), - a feedback-type component configured to modify the reducing agent dosing rate based at least partially on physical degradation of the SCR catalyst (152), and - an ammonia storage component configured to modify the reducing agent dosing rate based at least partially on a desired ammonia storage concentration on the SCR catalyst (152), wherein the desired ammonia storage concentration is an ammonia storage concentration that allows for transient changes in NO x -Emissions during temporary operating conditions of the internal combustion engine (11) are taken into account. [12] System according to claim 11, further comprising an AMOX catalyst (160) downstream of the SCR catalyst (152), wherein the feedback-type component is further configured to modify the reducing agent dosing rate based at least partially on physical degradation of the AMOX catalyst (160). [13] System according to claim 11, wherein the reducing agent is urea, wherein the urea is reduced partly to ammonia and partly to isocyanic acid before entering the SCR catalyst (152), and wherein the urea dosing rate is based at least partly on a first conversion efficiency of urea to ammonia and a second conversion efficiency of urea to isocyanic acid. [14] System according to claim 11, wherein the feedback-type component is further configured to modify the reducing agent dosing rate based at least partially on the occurrence of at least one reducing agent limiting condition. [15] System according to claim 14, wherein the at least one reducing agent limiting condition comprises an exhaust gas temperature limit, an ammonia slip limit and / or an SCR catalyst bed temperature limit. [16] System according to claim 11, wherein the desired ammonia storage concentration is based at least partially on a maximum ammonia storage capacity of the SCR catalyst (152). [17] System according to claim 12, wherein the desired ammonia storage concentration is based at least partially on a maximum ammonia storage capacity of the SCR catalyst (152) and a maximum NH3 conversion capability of the AMOX catalyst (160). [18] System according to claim 11, wherein the controller has an on-board diagnostic component configured to determine whether the SCR system (150) is able to measure the NO x -To reduce emissions in the exhaust stream to a quantity below a predetermined threshold. [19] System according to claim 18, further comprising an OBD interface (900) that can communicate electrically with the controller (130), wherein the controller (130) warns the OBD interface (900) when the OBD component determines that the SCR system (150) is unable to reduce the NO x -To reduce emissions in the exhaust stream to a quantity below the predetermined threshold. [20] System according to claim 18, wherein the determination of whether the SCR system (150) is able to reduce the NO x -Emissions in the exhaust stream to a quantity below a predetermined threshold, based at least partly on the physical degradation of the SCR catalyst (152). [21] System according to claim 11, wherein the SCR system (150) incorporates an NO embedded in the SCR catalyst (152). x -Sensor (164B) has. [22] System according to claim 21, wherein the SCR catalyst (152) comprises a pair of spaced-apart catalyst beds extending along a length of the SCR catalyst (152), wherein the catalyst beds define a space between the beds and wherein the embedded NO x -Sensor (164B) is positioned at least partially in the space between the beds.

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