WO2015183239A1

WO2015183239A1 - System and method for evaluation of aftertreatment fluid quality and deliverability

Info

Publication number: WO2015183239A1
Application number: PCT/US2014/039565
Authority: WO
Inventors: Aleksey Yezerets; Xu Chen
Original assignee: Cummins Inc.
Priority date: 2014-05-27
Filing date: 2014-05-27
Publication date: 2015-12-03

Abstract

Systems, methods and apparatus include determining a quality and/or deliverability of a reductant in an SCR catalyst aftertreatment system. During the diagnostic, a reductant amount corresponding to a diagnostic ammonia to NO_x ratio (ANR) value is injected, and an output of a NO_x sensor downstream of the SCR catalyst is compared to an expected output to diagnose a malfunction associated with the quality and/or deliverability of the reductant.

Description

SYSTEM AND METHOD FOR EVALUATION OF AFTERTREATMENT FLUID

QUALITY AND DELIVERABILITY

BACKGROUND

[0001] Presently available internal combustion engines require aftertreatment systems in many cases to meet stringent emissions requirements. Some aftertreatment systems require specific fluids for operation, such as diesel exhaust fluid (DEF) or urea, to be used as a reductant over a selective catalytic reduction (SCR) catalyst. The reductant is converted to ammonia (N¾) and works in conjunction with the SCR catalyst to react with oxides of nitrogen (NO_x) in the exhaust gas to reduce NO_x emissions.

[0002] In some situations, such as a pressure line that is kinked or other malfunction, the deliverability of the commanded amount of reductant may not be possible. In addition, these reductant fluids require re-filling from time -to-time due to consumption. Due to their expense, the aftertreatment fluid system may be subject to bypass or manipulation, and the type of fluid that is added to the system may be subject to varying quality, or the system may be filled with a fluid that is not a reductant. When the proper fluid is not present or has degraded quality, or the system is unable to deliver the commanded amount of reductant, the lack of ammonia on the SCR catalyst leads to reduced NO_x conversion and higher NO_x emissions. In some systems, poor reductant quality and/or deliverability may trigger on-board diagnostics (OBD), engine operations are de-rated to meet emissions requirements, and further may need to be reported for maintenance or regulatory requirements. While sensors may be employed for direct

measurement and verification of fluid quality, such sensors add cost and complexity to the OBD system. Therefore, further technological developments are desirable in this area. SUMMARY

[0003] The present application includes unique aftertreatment fluid quality determining apparatuses, systems, and methods. One embodiment includes operating an SCR aftertreatment system with at least one ammonia to NO_x ratio (ANR) input that is greater than five, determining an output of a NO_x sensor downstream of the SCR catalyst in response to the ANR input, and evaluating the output in comparison to an expected output to diagnose the quality and/or deliverability of the reductant. Another embodiment includes determining an expected NO_x conversion efficiency of the SCR catalyst, determining an expected output of a NO_x sensor downstream of the SCR catalyst in response to the expected NO_x conversion efficiency and a diagnostic ANR value that is at least five, and diagnosing at least one of a quality and deliverability of the reductant in response to a comparison of the actual NO_x sensor output to the expected NO_x sensor output.

[0004] This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views.

[0006] Fig. 1 is a schematic diagram of a system for determining a quality and/or deliverability of a reductant in an aftertreatment system.

[0007] Fig. 2 is a graph illustrating exemplary reductant quality/deliverability diagnostic data.

[0008] Fig. 3 is another graph illustrating exemplary reductant quality/deliverability diagnostic data.

[0009] Fig. 4 is a schematic diagram of an apparatus for determining a reductant quality.

[0010] Fig. 5 is a flowchart illustrating an exemplary reductant diagnostic procedure

DETAILED DESCRIPTION

[0011] For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated device, and any further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0012] Fig. 1 is a schematic diagram of a system 100 for determining an aftertreatment fluid quality. The system 100 includes an internal combustion engine 102 operable to produce an exhaust gas 116 into an exhaust flow path 118 connected to an aftertreatment system 120, where the exhaust gas 116 includes an amount of NO_x. The system 100 includes an SCR catalyst 104 for NO_x conversion that reduces at least a portion of the amount of NO_x before the exhaust gas 116 exits a tailpipe or other outlet downstream of SCR catalyst 104, a reductant source 108 that stores an amount of aftertreatment fluid such as a reductant 112, and a reductant injector 106 that receives the reductant 112 from the reductant source 108 and provides the reductant 112 to the exhaust gas 116 in exhaust flow path 118 at a position upstream of the SCR catalyst 104. The system 100 further includes at least one NO_x sensor 110 operably coupled to the exhaust flow path 118 and in communication with the exhaust gas 116 at a position downstream of the SCR catalyst 104.

[0013] NO_x sensor 110 is cross-sensitive to ammonia, and NH₃ that slips past SCR catalyst 104 is read by NO_x sensor 110 as NO_x. Although the precise amount of NH₃ that is read by the signal of NO_x sensor 110 as NO_x varies in response to operating conditions and other factors, for the purposes of determining the reductant quality and/or deliverability it can be assumed that one part NH₃ is read as one part NO_x by NO_x sensor 110.

[0014] The illustrated system 100 may be provided with a vehicle (not shown) such as a car, truck, bus, boat, recreational vehicle, construction equipment or another type of vehicle. Other embodiments include system 100 provided with other applications such as a pumping system or a generator set. System 100 may also include aftertreatment components not shown in addition to SCR catalyst 104, such as an oxidation catalyst in fluid communication with exhaust flow path 118 that is operable to catalyze oxidation of one or more compounds in exhaust gas 116 flowing through exhaust flow path 118, for example, oxidation of NO to N0₂. System 100 may further include a diesel particulate filter which is in fluid communication with exhaust flow path 118 and is operable to reduce the level of particulates in exhaust gas 116 flowing through exhaust flow path 118. In an exemplary embodiment the diesel particulate filter is a catalyzed soot filter. Other embodiments utilize other types of diesel particulate filters.

[0015] Exhaust flow path 118 is illustrated schematically in Fig. 1 and may be provided in a variety of physical configurations. In an exemplary embodiment exhaust flow path proceeds from the output of a turbocharger (not shown) of engine 102 through a conduit to a can or housing containing an oxidation catalyst and a diesel particulate filter, through a second conduit which includes a urea decomposition reactor, to a can or housing containing SCR catalyst 104 and an ammonia oxidation (AMOX) catalyst, which is operable to catalyze reaction of ammonia which slips past SCR catalyst 104, and through another conduit which outlets to the ambient environment. Other embodiments of aftertreatment system 120 omit one or more of the foregoing elements, include additional elements, feature alternate elements, and/or feature different arrangements and configurations of elements. [0016] The system 100 further includes a controller 114 that performs certain operations for determining an aftertreatment fluid quality and/or deliverability of the reductant 112. The reductant 112 may be ammonia, urea, urea with water, a diesel exhaust fluid, hydrogen, fuel, reformed fuel, or any other reducing agent understood in the art. In one embodiment, the reductant 112 is a urea- water mixture that is supposed to be a mixture having a specified ammonia concentration, or specified range of ammonia concentration, in which the urea decomposes in the exhaust flow path 118 to provide ammonia to SCR catalyst 104, which is operable to catalyze the reduction of NO_x.

[0017] The controller 114 includes modules structured to functionally execute operations to determine aftertreatment fluid quality and/or deliverability in conjunction with controlling reductant injector 106 to provide an amount of reductant such that the commanded ANR to the inlet of SCR catalyst 104 provides an ammonia amount that dominates the NO_x amount at the outlet of SCR catalyst 104. The outputs from NO_x sensor 110 can then be evaluated to determine whether the amount of ammonia that is provided at the outlet of SCR catalyst 104 in response to the ANR command results in a NO_x sensor output within range of an expected NO_x sensor output. If the actual NO_x sensor output deviates more than a threshold amount from the expected NO_x sensor output, then a reductant malfunction condition is determined and an error code or other malfunction in the quality and/or deliverability in the reductant can be output.

[0018] Referring to Fig. 2, there is shown a graph 200 which shows various ANR values along its x-axis and expected SCR outlet NO_x amounts to be measured by NO_x sensor 110 along the y- axis of graph 200, assuming the engine out (EO) NO_x amount is 1 and the exhaust flow is under steady state conditions in which SCR catalyst 104 is saturated with ammonia. Furthermore, the primary reaction over SCR catalyst 104 is that NO_x and NH₃ are converted to N₂, and other reactions are relatively insignificant. Since NO_x sensor 110 is cross sensitive to ammonia, the amount of NO_x and NH₃ present as NO_x sensor 110 will be recorded as NO_x.

[0019] For each of the ANR values, there is shown an expected SCR outlet NO_x amount to be read by NO_x sensor 110 in the two most extreme cases. In a first case SCR catalyst 104 removes all NO_x, as indicated by the 100% deNO_x efficiency values, and in a second case SCR catalyst 104 removes no NO_x, as indicated by the 0% deNO_x efficiency values. The differences between the two outputs in each case is shown to be 2 or less for all ANR values. A measurement variation in the illustrated example is determined by the ratio of a difference between high end and low end NO_x amounts at the SCR outlet to the NH₃ amount provided at the inlet of the SCR catalyst. At high ANR values, such as an ANR value of 10, the measurement variation of the NH₃ amount by NO_x sensor 110 due to the possible presence of NO_x is about 20%. Thus, when the ANR is high enough such that NH₃ dominates NO_x at NO_x sensor 110, the deNO_x efficiency of SCR catalyst 104 has a minor impact on the measurement variation of the SCR outlet NO_x amount since the NO_x signal from NO_x sensor 110 is dominated by NH₃ slip.

[0020] Graph 300 in Fig. 3 is based on upper and lower estimates of the deNO_x efficiency of SCR catalyst 104 likely to occur during actual nominal operations, ranging from 90% at a high end to 30% at a low end. In the Fig. 3 scenario, it is assumed that if the ANR is less than the deNO_x efficiency, then all NH₃ is converted to N₂. If the ANR is greater than the deNO_x efficiency, then all of the NO_x is assumed to be converted. As can be observed from graph 300, an ANR of around 6 provides a measurement variation of about 20% which corresponds to the measurement variation expected with an ANR of 10 in the extreme scenarios of 0% and 100% ΝΟχ conversion efficiency illustrated in Fig. 2. Accordingly, it is anticipated that a diagnostic ANR of 5 or more will provide sufficiently small measurement variation even if NO_x is present at NO_x sensor 110 for the determination of reductant quality and/or deliverability under nominal operating conditions.

[0021] In certain embodiments, the controller 114 includes a NO_x conversion efficiency module 402, a reductant status module 404, and a reductant quality determination module 406. More specific descriptions of the operations of the controller 114 for exemplary embodiments are included in the section referencing Fig. 4. The controller 114 may be a single device or a number of distributed devices, and the functions of the controller 114 may be performed by hardware and/or instructions stored on a non-transient computer readable medium.

[0022] Controller 114 is generally operable to control and manage operational aspects of system 100 including engine 102 and the exhaust aftertreatment system 120. Controller 114 includes memory as well as a number of inputs and outputs for interfacing with various sensors and systems of system 100. Controller 114 can be an electronic circuit comprised of one or more components, including digital circuitry, analog circuitry, or both. Controller 114 may be a software and/or firmware programmable type; a hardwired, dedicated state machine; or a combination of these. In one embodiment, controller 114 is of a programmable microcontroller solid-state integrated circuit type that includes memory and one or more central processing units. The memory of controller 114 can be comprised of one or more components and can be of any volatile or nonvolatile type, including the solid-state variety, the optical media variety, the magnetic variety, a combination of these, or other types of memory. Controller 114 can include signal conditioners, signal format converters (such as analog-to-digital and digital-to-analog converters), limiters, clamps, filters, and the like as needed to perform various control and regulation operations described herein. Controller 114, in an exemplary embodiment, may be a type of controller sometimes referred to as an electronic or engine control module (ECM), electronic or engine control unit (ECU) or the like, that is directed to the regulation and control of engine operation. Alternatively, controller 114 may be dedicated to control of just the operations described herein or to a subset of controlled aspects of system 100. In any case, controller 114 includes one or more control algorithms defined by operating logic in the form of software instructions, hardware instructions, firmware instructions, dedicated hardware, or the like. These algorithms will be described in greater detail hereinafter, for controlling operation of various aspects of system 100.

[0023] Controller 114 is in operative interconnection with various elements of system 100 as illustrated in Fig. 1 with dashed lines extending between controller 114 and various elements of system 100. These operative interconnections may be implemented in a variety of forms, for example, through input/output interfaces coupled via wiring harnesses. In other instances all or a portion of the operative interconnection between controller 114 and an element of system 100 may be virtual, for example, a virtual input indicative of an operating parameter may be provided by a model implemented by controller 114 or by another controller which models an operating parameter based upon other information.

[0024] Controller 114 is in operative communication with NO_x sensor 110 which provides controller 114 with information indicative of the level of NO_x and NH₃ output from SCR catalyst 104. In an exemplary embodiment NO_x sensor 110 is a physical sensor which is in fluid communication with exhaust flow path 118. Controller 114 is also in operative communication with a virtual NO_x sensor which provides controller 114 with information indicative of the level of NO_x input to SCR catalyst 104 using a model based upon operating conditions of engine 102, for example, engine load, engine fueling, exhaust temperature and/or other parameters. In other embodiments a NO_x sensor is provided upstream of SCR catalyst 104 that is a physical NO_x sensor which is in fluid communication with exhaust flow path 118 and is located upstream from SCR catalyst 104.

[0025] During operation controller 114 uses the information indicative of the level of NO_x provided to SCR catalyst 104 along with information from NO_x sensor 110 to determine the amount or rate of reductant to be injected by reductant injector 106. Controller 114 is in operative communication with reductant injector 106 and can command reductant injector 106 to inject selected amount of reductant or to inject reductant at a selected rate. In an exemplary embodiment controller 114 commands reductant injection that is determined to maximize the catalytic reduction of NO_x by SCR catalyst 104, to maximize ammonia storage by SCR catalyst 104, and to minimize the slip of ammonia past SCR catalyst 104. In other embodiments controller 114 commands reductant injection to differently balance these parameters or to account for additional or different parameters. As discussed further below, controller 114 is also operable to provide a reductant quality check dosing command to reductant injector 106 to inject a diagnostic reductant amount for diagnostic of reductant quality and/or deliverability in response to a reductant increase indicator in reductant source 108.

[0026] Controller 114 is in operative communication with a malfunction indicator 122 which is provided, for example, in an operator compartment of the vehicle and/or on any other suitable output device accessible by an operator and/or service technician. Malfunction indicator 122 can be a malfunction indicator light, or another type of display operable to provide information to the operator or service technician. Controller 114 is operable to command malfunction indicator 122 to display one or more indications based upon the diagnostics described herein, and may also store one or more error codes in a memory of a malfunction indicator 122 and/or in controller 114 or other output device based upon the diagnostics described herein. [0027] Fig. 4 is a schematic diagram of an apparatus 400 for determining an aftertreatment fluid quality. The apparatus 400 includes controller 114 having a NO_x conversion efficiency module 402, a reductant status module 404, and a reductant quality determination module 406 structured to functionally execute the operations of the controller 114. The description herein, including modules, emphasizes the structural independence of the aspects of the controller 114, and illustrates one grouping of operations and responsibilities of the controller 114. Other groupings that execute similar overall operations are understood within the scope of the present application. Modules may be implemented in hardware and/or instructions stored on a non-transient computer readable medium, and modules may be distributed across various hardware or non- transient computer readable medium components.

[0028] The NO_x conversion efficiency module 402 determines a NO_x conversion efficiency value 408 for the SCR catalyst 104. The NO_x conversion efficiency value 408 may be determined by any method understood in the art. Non-limiting examples include measuring or modeling a NO_x amount in the exhaust gas 116 upstream of the SCR catalyst 104 and measuring the NO_x amount in the exhaust gas 116 downstream of the SCR catalyst 104, for example with NO_x sensor 110, and determining the efficiency of SCR catalyst 104 in removing NO_x from exhaust gas 116. The NO_x conversion efficiency module 402 may receive the NO_x conversion efficiency value 408 as a datalink or network communication, and/or may read the NO_x conversion efficiency value 408 as a parameter stored on a computer readable medium.

[0029] The reductant status module 404 determines or receives a reductant level 410 and/or a ΝΟχ reductant fill indicator 412, and provides a reductant level increase indicator 414 in response to an increase in the reductant level. The reductant status module 404 may determine the reductant level 410 and/or a fill indicator 412 from a sensor level, from a fill indication value provided as a datalink or network communication, from reading a parameter stored on a computer readable medium, and/or from determining that a maintenance event of filling the reductant source 108 has occurred. For example, a maintenance parameter may be set by a computerized tool or a "pedal dance" after a filling of the reductant source 108 occurs. In other examples, a reductant level 410 may be tracked over time, and an increase amount greater than a nominal amount may be interpreted by the reductant status module 404 as a reductant increase indicator 414.

[0030] The reductant quality determination module 406 receives a reductant increase indicator 414 in response to an increase in the level of reductant source and determines if diagnostic enable conditions are present via a diagnostic conditions enable indicator 416. Diagnostic enable conditions indicator 416 can be TRUE for initiating the reductant quality diagnostic when operating conditions are satisfied that enable determination of the reductant quality and/or deliverability. Example and non-limiting enablement conditions can include the NO_x conversion efficiency of SCR catalyst 104 being between a lower threshold, such as 30%, and an upper threshold, such as 90%, the temperature of SCR catalyst being above a low temperature or light- off temperature threshold (such as a temperature between 300-400° C), the temperature of SCR catalyst being below an upper temperature threshold (such as a temperature between 500-600° C), and/or the exhaust flow rate being above a minimum flow threshold. When the diagnostic enable conditions are satisfied or TRUE, diagnostic enable conditions indicator 416 can be set to TRUE and the diagnostic of reductant quality and/or deliverability can proceed. If diagnostic enable conditions indicator 416 is FALSE, then a determination of reductant quality is not performed and delayed until the enable conditions are satisfied.

[0031] Reductant quality determination module 406 is further structured to receive a diagnostic ANR value 418 and an expected NO_x sensor output 420 in response to the diagnostic ANR value. The diagnostic ANR value 418 can be any value in which reductant is overdosed so that ammonia dominates NO_x at NO_x sensor 110. In one embodiment, the diagnostic ANR value 418 is 5 or more. In another embodiment, the diagnostic ANR value 418 is an ANR value in the range from 5 to 10. In a specific embodiment, the diagnostic ANR value is 6, which minimizes the measurement variation due to the potential for the presence of NO_x to around 20% while also minimizing the ammonia slippage from SCR catalyst 104 during the diagnostic. Expected NO_x sensor output 420 at the diagnostic ANR value 418 can be determined from the NO_x conversion efficiency value 408, the current amount of NO_x provided to the inlet of the SCR catalyst 104, and the diagnostic ANR value 418.

[0032] Reductant quality determination module 406 is further structured to determine the a reductant quality check dosing command 422 in response to the diagnostic ANR value 418 and control reductant injector 106 to dose an amount of reductant in response to the diagnostic ANR value 418 and the diagnostic enable conditions indicator 416 being TRUE. Reductant quality determination module 406 receives SCR outlet NO_x sensor output 424 from NO_x sensor 110 during the reductant diagnostic and compares SCR outlet NO_x sensor output 424 to expected NO_x sensor output 420. In response to a deviation of the SCR outlet NO_x sensor output 424 to expected NO_x sensor output 420 by more than a threshold amount, reductant quality

determination module 406 is configured to output a reductant quality indicator 426 to malfunction indicator 122. Malfunction indicator 122 can indicate that a malfunction in the reductant 112 has occurred due to the quality and/or deliverability of the reductant 112 from reductant source 108 failing or being non-compliant, and that insufficient ammonia is delivered for effective NO_x conversion across SCR catalyst 104. [0033] The permissible threshold deviation of the SCR outlet NO_x sensor output 424 from expected NO_x sensor output 420 can take into account the measurement variation in the ability of NO_x sensor 110 to measure the ammonia amount due to the possible presence of NO_x. For example, as discussed above, at a diagnostic ANR value 418 of 6, a measurement variation of up to 20% can be expected under nominal or expected operating conditions. Thus, a deviation of more than 20% can result in a malfunction output by reductant quality indicator 426. In addition, the permissible threshold deviation can account for an acceptable variation in the amount of ammonia in the reductant to be detected. For example, if the reductant 112 is a fluid that is 32.5%) urea by weight, and a solution of 25% urea by weight is the accepted level of variability, the threshold deviation can further account for the deviation in the NO_x sensor output 424 from expected NO_x sensor output 420 hat is normally expected to occur from a 25% urea solution being utilized instead of a 32.5% urea solution. The reductant quality determination module 406 may also utilize multiple diagnostic ANR values 418 in a diagnostic test to determined reductant quality indicator 426.

[0034] The outputs described for the reductant quality indicator 426 are exemplary and non- limiting. Equivalent outputs, names conveying similar information, and numbers stored on computer readable medium that have a translatable meaning to indicate reductant quality and/or deliverability information are contemplated herein.

[0035] An exemplary procedure 500 for determining a reductant quality is described with reference to Fig. 5. Fig. 5 is a flowchart illustrating an exemplary diagnostic procedure 500. Procedure 500 may be implemented by controller 114 of system 100 described above or in another controller. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or part, unless stated explicitly to the contrary herein. Certain operations illustrated may be implemented by a computer executing a computer program product on a computer readable medium, where the computer program product comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.

[0036] The exemplary procedure includes an operation 502 to determining a first parameter value corresponding to a first NO_x conversion efficiency value of SCR catalyst 104. The procedure further includes a conditional 504 to determine if a reductant level in reductant source 108 has increased a threshold amount. If conditional 504 is negative, then procedure 500 returns to operation 502. If conditional 504 is positive, procedure 500 continues at conditional 506 to determine if operating conditions are present to enable a diagnostic of the reductant are satisfied. If conditional 506 is negative, procedure 500 returns to operation 502 but maintains the reductant level increase event flag as true until operating conditions are present that enable a reductant quality diagnostic.

[0037] If conditional 506 is true, procedure 500 continues at operation 508 to determine a diagnostic ANR value, which may be a predetermined or programmed value, or determined as a function of operating conditions. Procedure 500 continues at operation 510 to determine an expected NO_x sensor output for NO_x sensor 110. Procedure 500 continues from operation 510 at operation 512 to command the reductant injector 106 to provide reductant 112 from reductant source 108 into the exhaust flow path 118 in response to the diagnostic ANR value. The procedure further includes an operation 514 to determine the output of the NO_x sensor 110 in response to the diagnostic ANR value being injected into the exhaust gas 116. Procedure 500 continues at conditional 516 to compare the NO_x sensor output to the expected NO_x sensor output. Procedure 500 includes an operation 518 to determine the reductant quality indicator as failed or non-compliant in response to a deviation of NO_x sensor output from the expected NO_x sensor output by more than a threshold amount. If the NO_x sensor output deviates from the expected NO_x sensor output by more than a threshold amount, then an error code can be provided and the reductant quality indicator indicates a malfunction in the quality and/or deliverability of the reductant as failed or non-compliant. Procedure 500 may also include an operation 520 to determine the reductant quality indicator as passed or compliant in response to a deviation of NO_x sensor output from the expected NO_x sensor output by less than the threshold amount. If the deviation is less than the threshold amount then the reductant quality indicator can indicate the quality and/or deliverability of the reductant as passed or compliant.

[0038] As is evident from the figures and text presented above, a variety of embodiments according to the present invention are contemplated.

[0039] According to one aspect, a method includes operating an aftertreatment system including a SCR catalyst and a reductant injector connected to a reductant source, the aftertreatment system further including a NO_x sensor downstream of the SCR catalyst; determining an increase in a reductant level of the reductant source; in response to the increase, injecting a reductant amount into an exhaust gas in the aftertreatment system from the reductant source, the reductant amount corresponding to a diagnostic ANR value that is at least 5; comparing an output of the NO_x sensor to an expected output of the NO_x sensor in response to injecting the reductant; and determining a reductant quality indicator in response to the comparing.

[0040] In one embodiment, the diagnostic ANR value is in the range from 5 to 10. In another embodiment, the diagnostic ANR value is 6. In yet another embodiment, the diagnostic ANR value ranges from 5 to 20. In still another embodiment, the diagnostic ANR value ranges from 2 to 20. In another embodiment, the reductant is urea.

[0041] In a further embodiment, the method includes at least one of storing an error code and actuating a malfunction indicator in response to the comparing indicating the output of the NO_x sensor deviates from the expected output of the NO_x sensor by more than a threshold amount. In another embodiment, the method includes determining a NO_x conversion efficiency of the SCR catalyst and determining the expected output of the NO_x sensor in response to the NO_x conversion efficiency, an amount of NO_x being provided to an inlet of the SCR catalyst, and the diagnostic ANR value.

[0042] In another embodiment, the method includes determining operating conditions of the aftertreatment system enable injecting the reductant at the diagnostic ANR value. In a refinement of this embodiment, the operating conditions include at least one of a temperature of the SCR catalyst being above a low temperature threshold, the temperature of the SCR catalyst being below an upper temperature threshold, and a flow rate of the exhaust gas being above a low flow threshold.

[0043] According to another aspect, a system includes an internal combustion engine connected to an exhaust flow path, a SCR catalyst in fluid communication with the exhaust flow path, a reductant injector configured to inject a reductant from a reductant source into the exhaust flow path upstream of the SCR catalyst, and a NO_x sensor in connected to the exhaust flow path downstream of the SCR catalyst. The system also includes a controller operable to receive signals from the NO_x sensor and provide reductant dosing commands to the reductant injector. The controller is structured to perform a diagnostic routine that includes determining a reductant level increase in the reductant source and, in response to the reductant level increase, commanding the reductant injector to inject a reductant amount corresponding to a diagnostic ANR value of at least 5, receiving a NO_x sensor output from the NO_x sensor in response to injection of the reductant amount, and diagnosing at least one of a quality and deliverability of the reductant in response to a comparison of the NO_x sensor output to an expected NO_x sensor output.

[0044] In one embodiment, the controller is structured to initiate the diagnostic routine in response to at least one enable condition being satisfied. In a refinement of this embodiment, the at least one enable condition includes at least one of a temperature of the SCR catalyst being above a low temperature threshold, the temperature of the SCR catalyst being below an upper temperature threshold, and a flow rate of the exhaust gas being above a low flow threshold.

[0045] In another embodiment, the controller is structured to determine a NO_x conversion efficiency of the SCR catalyst. In a refinement of this embodiment, the controller is structured to determine the expected NO_x sensor output as a function of the diagnostic ANR value, the NO_x conversion efficiency, and a NO_x amount to the SCR catalyst.

[0046] In another embodiment, the diagnostic ANR value is in the range from 5 to 10. In a further embodiment, the reductant is urea. In yet another embodiment, the controller is structured to store an error code and command a malfunction indicator to provide an indication of a reductant malfunction in response to the output of the NO_x sensor deviating from the expected output of the NO_x sensor by more than a threshold amount

[0047] In another aspect, an apparatus includes a controller operably connectable to at least one NO_x sensor downstream of a SCR catalyst and to a reductant injector upstream of the SCR catalyst, the reductant injector further being connected to a reductant source containing a reductant. The controller includes a reductant status module structured to determine one of a reductant level and a reductant fill indicator, and to provide a reductant level increase indicator in response to an increase in a reductant level in the reductant source. The controller also includes a reductant quality determination module structured to determine a reductant quality check dosing command in response to the reductant level increase indicator for injection of a reductant amount corresponding to a diagnostic ANR value that is at least 5, the reductant quality determination module further being structured to compare an output of the NO_x sensor to an expected NO_x sensor output in response to injection of the reductant amount and determine a reductant quality indicator in response to a deviation of the output of the NO_x sensor from the expected NO_x sensor output.

[0048] In one embodiment, the controller further comprises a NO_x conversion efficiency module structured to determine a NO_x conversion efficiency value for the SCR catalyst. In a refinement of this embodiment, the controller is configured to determine the expected NO_x sensor output as a function of the diagnostic ANR value, the NO_x conversion efficiency value, and a NO_x amount at an inlet of the SCR catalyst. In another embodiment, the controller is structured to determine a malfunction associated with at least one of the quality and deliverability of the reductant in response to the deviation exceeding a threshold amount.

[0049] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. [0050] In reading the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

operating an aftertreatment system including a selective catalytic reduction (SCR) catalyst and a reductant injector connected to a reductant source, the aftertreatment system further including a NO_x sensor downstream of the SCR catalyst;

determining an increase in a reductant level of the reductant source;

in response to the increase, injecting a reductant amount into an exhaust gas in the aftertreatment system from the reductant source, the reductant amount corresponding to a diagnostic ammonia to NO_x ratio (ANR) value that is at least 5;

comparing an output of the NO_x sensor to an expected output of the NO_x sensor in response to injecting the reductant; and

determining a reductant quality indicator in response to the comparing.

2. The method of claim 1 , wherein the diagnostic ANR value is in the range from 5 to 10.

3. The method of claim 1, wherein the diagnostic ANR value is 6.

4. The method of claim 1, further comprising at least one of storing an error code and actuating a malfunction indicator in response to the comparing indicating the output of the NO_x sensor deviates from the expected output of the NO_x sensor by more than a threshold amount.

5. The method of claim 1 , wherein the reductant is urea.

6. The method of claim 1, further comprising determining a NO_x conversion efficiency of the SCR catalyst and determining the expected output of the NO_x sensor in response to the NO_x conversion efficiency, an amount of NO_x being provided to an inlet of the SCR catalyst, and the diagnostic ANR value.

7. The method of claim 1, further comprising determining operating conditions of the aftertreatment system enable injecting the reductant at the diagnostic ANR value.

8. The method of claim 7, wherein the operating conditions include at least one of a temperature of the SCR catalyst being above a low temperature threshold, the temperature of the SCR catalyst being below an upper temperature threshold, and a flow rate of the exhaust gas being above a low flow threshold.

9. A system comprising:

an internal combustion engine connected to an exhaust flow path;

an selective catalytic reduction (SCR) catalyst in fluid communication with the exhaust flow path;

a reductant injector configured to inject a reductant from a reductant source into the exhaust flow path upstream of the SCR catalyst;

a NO_x sensor in connected to the exhaust flow path downstream of the SCR catalyst; and a controller operable to receive signals from the NO_x sensor and provide reductant dosing commands to the reductant injector, the controller structured to perform a diagnostic routine, the diagnostic routine including determining a reductant level increase in the reductant source and, in response to the reductant level increase, commanding the reductant injector to inject a reductant amount corresponding to a diagnostic ammonia to NO_x ratio (ANR) value of at least 5, receiving a NO_x sensor output from the NO_x sensor in response to injection of the reductant amount, and diagnosing at least one of a quality and deliverability of the reductant in response to a comparison of the NO_x sensor output to an expected NO_x sensor output.

10. The system of claim 9, wherein the controller is structured to initiate the diagnostic routine in response to at least one enable condition being satisfied.

11. The system of claim 10, wherein the at least one enable condition includes at least one of a temperature of the SCR catalyst being above a low temperature threshold, the temperature of the SCR catalyst being below an upper temperature threshold, and a flow rate of the exhaust gas being above a low flow threshold.

12. The system of claim 9, wherein the controller is structured to determine a NO_x conversion efficiency of the SCR catalyst.

13. The system of claim 12, wherein the controller is structured to determine the expected NO_x sensor output as a function of the diagnostic ANR value, the NO_x conversion efficiency, and a NO_x amount to the SCR catalyst.

14. The system of claim 9, wherein the diagnostic ANR value is in the range from 5 to 10.

15. The system of claim 9, wherein the reductant is urea.

16. The system of claim 9, wherein the controller is structured to store an error code and command a malfunction indicator to provide an indication of a reductant malfunction in response to the output of the NO_x sensor deviating from the expected output of the NO_x sensor by more than a threshold amount

17. An apparatus, comprising:

a controller operably connectable to at least one NO_x sensor downstream of a selective catalytic reduction (SCR) catalyst and to a reductant injector upstream of the SCR catalyst, the reductant injector further being connected to a reductant source containing a reductant, the controller comprising:

a reductant status module structured to determine one of a reductant level and a reductant fill indicator, and to provide a reductant level increase indicator in response to an increase in a reductant level in the reductant source; and

a reductant quality determination module structured to determine a reductant quality check dosing command in response to the reductant level increase indicator for injection of a reductant amount corresponding to a diagnostic ammonia to NO_x ratio (ANR) value that is at least 5, the reductant quality determination module further being structured to compare an output of the NO_x sensor to an expected NO_x sensor output in response to injection of the reductant amount and determine a reductant quality indicator in response to a deviation of the output of the NO_x sensor from the expected NO_x sensor output.

18. The apparatus of claim 17, where the controller further comprises a NO_x conversion efficiency module structured to determine a NO_x conversion efficiency value for the SCR catalyst.

19. The apparatus of claim 18, wherein the controller is structured to determine the expected NO_x sensor output as a function of the diagnostic ANR value, the NO_x conversion efficiency value, and a NO_x amount at an inlet of the SCR catalyst.

20. The apparatus of claim 17, wherein the controller is structured to determine a malfunction associated with at least one of the quality and deliverability of the reductant in response to the deviation exceeding a threshold amount.