Vehicle and a method of updating efficiency of a selective catalytic reduction filter of an exhaust treatment system of the vehicle

A vehicle and a method of updating efficiency of a selective catalytic reduction filter (SCRF) of an exhaust treatment system of the vehicle are disclosed. The method includes obtaining an initial calculated efficiency of the SCRF, via a controller, regarding one of a NOx conversion, a reductant absorption, a reductant desorption and a reductant oxidation. The method also includes determining a soot mass estimate in the SCRF representative of an amount of soot collected inside the SCRF and determining a soot correction factor from the soot mass estimate. The method further includes calculating, via the controller, an updated efficiency value of the SCRF by multiplying the soot correction factor and the initial calculated efficiency to update efficiency of the SCRF.

TECHNICAL FIELD

The present disclosure relates to a vehicle and a method of updating efficiency of a selective catalytic reduction filter of an exhaust treatment system of the vehicle.

BACKGROUND

Internal combustion engines can produce byproducts of the fuel combustion process, including various oxides of nitrogen, referred to collectively herein as NOx gases. Exhaust gas treatment systems can be used in vehicles to treat the NOx gases created in the combustion process.

Exhaust gas treatment systems generally include a selective catalytic reduction (SCR) device to reduce NOx gases. The SCR device uses a reductant capable of reacting with NOx gases to convert the NOx gases into inert byproducts, i.e., nitrogen and water. For example, the reductant can be an aqueous solution of urea, which is injected into the engine's exhaust stream. Once the reductant is in the exhaust stream, the reductant is absorbed into a catalyst of the SCR device, where the catalytic action of the SCR device ultimately converts NOx gases into the inert byproducts.

Exhaust gas treatment systems also include a diesel particulate filter (DPF) to filter out particles or particulate matter in the exhaust stream that is emitted by the engine. Generally, the DPF captures or traps sooty particulate matter and other suspended particulate matter from the exhaust stream. For example, the particulate matter can include carbonaceous soot particulates that can be oxidized to produce gaseous carbon dioxide, as well as other non-combustible particulates (i.e., ash) that are not capable of being oxidized.

Generally, the SCR device is spaced from the DPF such that the SCR device and the DPF are separate and independent components. Therefore, the SCR device converts NOx gases into the inert byproducts independently of the particulate matter being trapped by the DPF.

In-situ thermal regeneration of the DPF can be conducted periodically to burn off the accumulated particulate matter. However, thermal regeneration cannot remove ash from the DPF, and therefore, ash continues to accumulate in the DPF throughout the life of the DPF.

SUMMARY

The present disclosure provides a method of updating efficiency of a selective catalytic reduction filter (SCRF) of an exhaust treatment system of a vehicle. The method includes obtaining an initial calculated efficiency of the SCRF, via a controller, regarding one of a NOx conversion, a reductant absorption, a reductant desorption and a reductant oxidation. The method also includes determining a soot mass estimate in the SCRF representative of an amount of soot collected inside the SCRF and determining a soot correction factor from the soot mass estimate. The method further includes calculating, via the controller, an updated efficiency value of the SCRF by multiplying the soot correction factor and the initial calculated efficiency to update efficiency of the SCRF.

The present disclosure also provides a vehicle including an engine that generates an exhaust stream during operation and an exhaust treatment system coupled to the engine. The exhaust treatment system includes a selective catalytic reduction filter (SCRF) to catalytically convert constituents in the exhaust stream into inert byproducts and to filter particulate matter from the exhaust stream. The exhaust treatment system further includes a controller in communication with the SCRF, with the controller including a processor and a memory having recorded instructions for updating efficiency of the SCRF of the exhaust treatment system. The controller is configured to obtain an initial calculated efficiency of the SCRF regarding one of a NOx conversion, a reductant absorption, a reductant desorption and a reductant oxidation. The controller is also configured to determine a soot mass estimate in the SCRF representative of an amount of soot collected inside the SCRF and determine a soot correction factor from the soot mass estimate. The controller is further configured to calculate, via a controller, an updated efficiency value of the SCRF by multiplying the soot correction factor and the initial calculated efficiency to update efficiency of the SCRF.

Therefore, various particulate matter, such as soot is taken into consideration to determine the updated efficiency of the SCRF, and thus, optimize the exhaust treatment system. By accounting for various particulate matter in the SCRF, various models can be more accurately calibrated to maximize NOx reduction efficiencies and minimize expelling the reductant out of the SCRF. Furthermore, accounting for various particulate matter in the SCRF can optimize emissions, diagnostics, reductant consumption and fuel economy of the vehicle. Additionally, reductant consumption can be more accurately calibrated.

The detailed description and the drawings or Figures are supportive and descriptive of the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claims have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a vehicle10is generally shown inFIG. 1. The vehicle10includes an engine12that generates an exhaust stream14(arrow14) during operation. The engine12can be an internal combustion engine such as a diesel engine or any other engine that emits gases, such as oxides of nitrogen (NOx), i.e., NOx gases, into the exhaust stream14. An exhaust gas tube16is coupled to the engine12and receives the exhaust gas from the engine12such that the exhaust stream14moves through the exhaust gas tube16. While a diesel engine application is described hereinafter for illustrative purposes only, those skilled in the art will appreciate that a similar approach can be taken with other engine12designs.

The vehicle10includes an exhaust treatment system18coupled to the engine12. The exhaust treatment system18treats various constituents in the exhaust gas such as NOx gases. In other words, the exhaust treatment system18treats various emissions contained in the exhaust stream14expelled from the engine12.

As shown inFIG. 1, the vehicle10includes a tank20for storing fuel, such as, for example, diesel fuel. The diesel fuel is drawn from the tank20and combusted in the engine12which generates the exhaust stream14, and the exhaust stream14is then processed through the exhaust treatment system18before being expelled from a tailpipe22.

The exhaust system18includes a series of exhaust after-treatment devices24,26, shown inFIG. 1as an oxidation catalyst24, such as a diesel oxidation catalyst24(DOC), and a selective catalyst reduction filter26(SCRF) which are each discussed in detail below.

Accordingly, the exhaust gas tube16directs the exhaust gas stream14from the engine12through the series of exhaust after-treatment devices24,26. Depending on the embodiment, the after-treatment devices24,26of the exhaust system18can be arranged in other orders than shown inFIG. 1. Collectively, the DOC24and the SCRF26condition the exhaust stream14.

As discussed above, the exhaust after-treatment devices24,26are utilized to reduce various exhaust emissions of the engine12. For example, the DOC24receives the exhaust gas stream14from the engine12to oxidize and burn hydrocarbon emissions present in the exhaust stream14. The DOC24is in communication with a fuel injection device that delivers a calibrated amount of fuel into the DOC24. Ignition of the injected fuel rapidly increases the temperature of the exhaust stream14, generally 600° C. (Celsius) or higher, in order to enable a thermal regeneration of the SCRF26.

In one example, following the DOC24, the exhaust stream14is routed to the SCRF26. In other words, the SCRF26is disposed downstream to the DOC24. Generally, the SCRF26catalytically converts constituents in the exhaust stream14into inert byproducts and filters particulate matter from the exhaust stream14. In other words, the SCRF26treats various emissions contained in the exhaust stream14and also filters particulate matter, such as soot and ash, from the exhaust stream14. Therefore, generally, the SCRF26performs multiple functions, such as, treating NOx gases and filtering soot and ash from the exhaust stream14(each of which are discussed in turn below). Simply stated, SCRF26is utilized to reduce NOx emissions and particulate matter expelled from the engine12powering the vehicle10.

Continuing withFIG. 1, the SCRF26includes an active catalytic component28, referred to herein as a catalyst28. The catalyst28can be an oxide of a base metal such as vanadium, molybdenum, tungsten and zeolite. A reductant30is utilized to convert NOx gases into inert byproducts. As such, the SCRF26is converting NOx gases with the aid of the catalyst28into inert byproducts, i.e., diatomic nitrogen N2, and water H2O. The reductant30can be an anhydrous ammonia, aqueous ammonia, ammonia precursors, aqueous solution of urea or any other suitable reductant30, which is added to the exhaust stream14and absorbed in the SCRF26. An injector32(seeFIG. 1) or any other suitable device can be utilized to add the reductant30to the exhaust stream14.

Exhaust emissions of both gasoline engines12and diesel engines12can be optimized by utilizing the SCRF26. For the diesel engine12embodiment, the reductant30can be a diesel-exhaust-fluid (DEF) that is used in SCRF26. Accordingly, the DEF is disposed on the catalyst28of the SCRF26as the exhaust gas stream14flows through SCRF26.

Referring toFIG. 1, the SCRF26can include a carrier or substrate34that is dipped into a washcoat36containing the active catalytic component28, i.e., the catalyst28. Generally, the washcoat36is applied to or coated on a surface of the substrate34for absorbing the reductant30. More specifically, the substrate34is porous and the washcoat36is applied or coated on the surface of the substrate34within the pores. The substrate34can be a ceramic brick or a ceramic honeycomb structure, a plate structure, or any other suitable structure. In other words, the washcoat36can be applied to the surface of the pores of ceramic brick. For example, the substrate34can be formed of silicon carbide (SiC), cordierite or any other suitable substrate being highly porous. The washcoat36attracts the reductant30to deposit the reductant30in the SCRF26. In other words, the reductant30is disposed on the washcoat36inside the SCRF26. As the exhaust stream14passes through the SCRF26, the reductant30interacts with the exhaust gas stream14to generate a chemical reaction which reduces NOx gases passing through the exhaust system18.

As the exhaust gas stream14passes through the SCRF26, the particulate matter emitted from the engine12is collected in the SCRF26. Therefore, the SCRF26can include a filter38(seeFIG. 1) for collecting the particulate matter. As such, for example, the filter38of the SCRF26collects sooty particulate matter during a soot loading phase and disposes of the sooty particulate matter through the regeneration process. Generally, carbonaceous soot particulates can be oxidized during the regeneration process to produce gaseous carbon dioxide. The efficiency of the SCRF26can be degraded due to an amount of soot accumulated on the SCRF26, during the soot loading phase leading up to the regeneration process. In other words, the combustible particulate matter, such as soot, can build on the surface of the SCRF26which can degrade the efficiency of the SCRF26. In-situ thermal regeneration of the SCRF26can be conducted periodically to burn off accumulated sooty particulate matter. In other words, when a predetermined amount of soot builds inside the SCRF26, thermal regeneration can be conducted to remove the soot from inside the SCRF26. Therefore, over the life of the SCRF26, many thermal regenerations can be performed to the SCRF26to periodically remove soot.

Furthermore, as the exhaust gas stream14passes through the SCRF26, the SCRF26collects other non-combustible particulates (i.e., ash) emitted from the engine12. In other words, the filter38of the SCRF26collects particulate matter such as ash. For example, ash can form as a result of oil being burned during the engine combustion process. However, the other non-combustible particulates, such as ash, are not capable of being oxidized during the regeneration process. Therefore, ash accumulates inside the SCRF26after each thermal regeneration removing soot. Specifically, ash continues to accumulate in the filter38of the SCRF26throughout the life of the SCRF26. In other words, ash cannot be removed from the SCRF26unless the SCRF26is removed from the vehicle10. Therefore, ash builds inside of the SCRF26throughout the life of the SCRF26. As the ash builds inside the filter38, the ash can accumulate on the surface of the substrate34, thus reducing the area of the washcoat36to react with the reductant30. Therefore, the efficiency of the SCRF26can be degraded due to an amount of ash accumulation on the SCRF26. In other words, ash can build inside the SCRF26which can degrade the efficiency of the SCRF26.

Continuing withFIG. 1, the exhaust system18can further include at least one NOx sensor40. In one embodiment, the NOx sensor40can be positioned upstream to the SCRF26. For example, the NOx sensor40can be positioned upstream to the DOC24and the SCRF26such that the NOx sensor40is disposed between the engine12and the DOC24. As another example, the NOx sensor40can be positioned upstream to the SCRF26such that the NOx sensor40is disposed between the DOC24and the SCRF26. In another embodiment, the NOx sensor40can be positioned downstream to the SCRF26. For example, the NOx sensor40can be positioned between the SCRF26and the tailpipe22. In another embodiment, the NOx sensor40can be defined as a plurality of NOx sensors40, with one of the NOx sensors40positioned upstream to the DOC24and another one of the NOx sensors40positioned downstream to the SCRF26. Structurally and functionally, the NOx sensors40can be different or identical.

The exhaust system18can further include a controller42(seeFIG. 1) in communication with various components of the vehicle10. For example, the controller42is in communication with the SCRF26. As another example, the controller42can be in communication with each of the NOx sensors40. Therefore, the NOx sensors40can send or communicate NOx level measurements to the controller42. The controller42can be a stand-alone unit, or be part of an electronic controller42that regulates the operation of the engine12. The controller42can include a processor44and a memory46having recorded instructions for updating efficiency of the SCRF26of the exhaust treatment system18, as discussed further below. For example, the controller42can be a host machine or distributed system, e.g., a computer such as a digital computer or microcomputer, acting as a vehicle control module, and/or as a proportional-integral-derivative (PID) controller device having a processor, and tangible, non-transitory memory such as read-only memory (ROM) or flash memory. The controller42can also have random access memory (RAM), electrically erasable programmable read only memory (EEPROM), a high-speed clock, analog-to-digital (A/D) and/or digital-to-analog (D/A) circuitry, and any required input/output circuitry and associated devices, as well as any required signal conditioning and/or signal buffering circuitry. Therefore, the controller42can include all software, hardware, memory46, algorithms, connections, sensors, etc., necessary to monitor and control the exhaust treatment system18and the engine12. As such, a control method operative to evaluate and update the efficiency of the SCRF26can be embodied as software or firmware associated with the controller42. Furthermore, the control method operative to evaluate and initiate a regeneration can be embodied as software or firmware associated with the controller42. It is to be appreciated that the controller42can also include any device capable of analyzing data from various sensors, comparing data, making the necessary decisions required to control and monitor the exhaust treatment system18.

Furthermore, the exhaust system18can include a particulate filter sensor48(seeFIG. 1) that measures the differential pressure across the SCRF26. In other words, the particulate filter sensor48can measure a pressure difference50(seeFIGS. 3-6) in the SCRF26. Generally, the controller42can be in communication with the particulate filter sensor48. Therefore, the particulate filter sensor48can send or communicate the pressure difference50across the SCRF26. The particulate filter sensor48measures and calculates the pressure difference50between an inlet side52and an outlet side54of the SCRF26. The particulate filter sensor48can be a unitary sensor or gauge connected to the SCRF26. Alternatively, the particulate filter sensor48can be embodied as a pair of pressure taps that individually read the inlet and outlet pressures, and then calculates the pressure difference50across the SCRF26. The particulate filter sensor48can return a resultant pressure measurement to the controller42.

Additionally, the exhaust system18can include a temperature sensor56(seeFIG. 1) that measures a temperature58(seeFIGS. 3-6) of the substrate34of the SCRF26. Generally, the controller42can be in communication with the temperature sensor56. Therefore, the temperature sensor56can send or communicate the temperature58of the substrate34to the controller42. It is to be appreciated that more than one temperature sensor56can be utilized with the exhaust system18.

After the exhaust gas stream14exits the SCRF26, the exhaust stream14passes through the tailpipe22. In other words, the tailpipe22is disposed downstream of the SCRF26. In one embodiment, the SCRF26is disposed between the DOC24and the tailpipe22.

Various inputs can be communicated to and from the controller42. These inputs can be inputted into one or more models60,62,64,66within the controller42. For example, the controller42can store one or more of a NOx model60, an absorption model62, a desorption model64and an oxidation model66. The NOx model60stores information regarding the SCRF26catalytically converting constituents in the exhaust stream14into inert byproducts. The absorption model62stores information regarding absorption of the reductant30on the substrate34of the SCRF26. The desorption model64stores information regarding desorption of the reductant30through the SCRF26. The oxidation model66stores information regarding the oxidizing of the reductant30through the SCRF26. Therefore, various information or inputs are relayed to the controller42which can be utilized for the NOx model60, the absorption model62, the desorption model64and the oxidation model66. As ash and soot collects inside the SCRF26, the area of the surface (of the substrate34) presenting the catalyst28that absorbs the reductant30is reduced. In other words, as the ash and soot collects inside the SCRF26, some of the washcoat36(including the catalyst28) is covered by the ash/soot which decreases the area of the washcoat36being able to absorb the reductant30. Accordingly, the models60,62,64,66capture and account for ash/soot accumulation inside the SCRF26. As such, various efficiencies can be updated utilizing the controller42.

Referring toFIG. 2, the present disclosure provides a method1000of updating efficiency of the SCRF26of the exhaust treatment system18of the vehicle10. As such, the method1000updates the efficiency for one or more of the NOx model60, the absorption model62, the desorption model64and the oxidation model66as discussed above.

The method1000includes obtaining1002an initial calculated efficiency68of the SCRF26, via the controller42, regarding one of a NOx conversion, a reductant absorption, a reductant desorption and a reductant oxidation. In other words, the controller42obtains or collects the initial calculated efficiency68of the SCRF26. The initial calculated efficiency68regarding the NOx conversion is illustrated inFIG. 3in the NOx model60. The initial calculated efficiency68regarding the reductant absorption is illustrated inFIG. 4in the absorption model62. The initial calculated efficiency68regarding the reductant desorption is illustrated inFIG. 5in the desorption model64. The initial calculated efficiency68regarding the reductant oxidation is illustrated inFIG. 6in the oxidation model66. The initial calculated efficiency68can be calculated using numeric data obtained either through empirical testing or through analytic formulation which is discussed further below.

The method1000also includes determining1004a soot mass estimate70in the SCRF26representative of an amount of soot collected inside the SCRF26and determining1006a soot correction factor72from the soot mass estimate70. The method1000further includes calculating1008, via the controller42, an updated efficiency value74of the SCRF26by multiplying the soot correction factor72and the initial calculated efficiency68to update the efficiency of the SCRF26, i.e., to obtain an updated efficiency of the SCRF26. An amount of the reductant30being passed into the exhaust stream14can be adjusted based on the updated efficiency of the SCRF26. It is to be appreciated that the controller42can store one or more of the mathematical calculations ofFIGS. 3-6to update the desired efficiency of the SCRF26as discussed further below.

The soot mass estimate70in the SCRF26can be determined by utilizing various inputs. One of the inputs that can be utilized is the pressure difference50across the SCRF26. Another one of the inputs that can be utilized is the temperature58of the substrate34of the SCRF26. Another one of the inputs that can be utilized is a total time76since a thermal regeneration being performed to the SCRF26. If more than one thermal regeneration has been performed to the SCRF26, the total time76is from the last thermal regeneration performed to the SCRF26.

Therefore, in certain embodiments, determining1004the soot mass estimate70in the SCRF26can include determining the pressure difference50across the SCRF26. Furthermore, in certain embodiments, determining1004the soot mass estimate70in the SCRF26can include determining the temperature58of the substrate34of the SCRF26. Additionally, in certain embodiments, determining1004the soot mass estimate70in the SCRF26can include determining the total time76since the thermal regeneration being performed to the SCRF26. As such, determining1004the soot mass estimate70in the SCRF26can include selecting a first numeric value from a look-up table78based on at least one of the pressure difference50across the SCRF26, the temperature58of the substrate34and the total time76since the thermal regeneration. Selecting the first numeric value from the look-up table78based on at least one of the pressure difference50, the temperature58of the substrate34and the total time76since the thermal regeneration should be construed to include non-exclusive logical “or”, i.e., at least one of the pressure difference50across the SCRF26or the temperature58of the substrate34of the SCRF26or the total time76since the last thermal regeneration performed to the SCRF26or combinations thereof, which are discussed further below. Furthermore, it is to be appreciated that other inputs can be utilized to determine the soot mass estimate70, such as for example, pressures, NOx levels, the total miles the vehicle10has traveled, time, etc. As indicated above, it is to be appreciated that the one or a combination of more than one of the pressure difference50across the SCRF26, the temperature58of the substrate34of the SCRF26, the total time76since the last thermal regeneration performed to the SCRF26, etc., can be utilized to determine the soot mass estimate70. It is to be appreciated that the look-up table78can be populated using numeric data obtained either through empirical testing or through analytic formulation. In certain embodiments, the soot mass estimate70can be a value expressed in grams of soot.

The initial calculated efficiency68can be inputted into various models60,62,64,66as discussed above. Each of the models60,62,64,66are discussed in turn below.

Referring toFIG. 3, for the NOx model60, the initial calculated efficiency68is further defined as one of an initial NOx conversion efficiency80representing the ability of the SCRF26to catalytically convert constituents in the exhaust stream14into inert byproducts regarding the NOx conversion. For example, various inputs can be utilized to obtain the initial calculated efficiency68of the NOx conversion. One of the inputs that can be utilized is the temperature58of the substrate34of the SCRF26. Another one of the inputs that can be utilized is an exhaust flow rate82through the SCRF26. In other words, the flow rate of the exhaust gas stream14through the SCRF26. Yet another one of the inputs that can be utilized is an amount of reductant stored84on the washcoat36of the substrate34of the SCRF26. Yet another one of the inputs that can be utilized is a maximum reductant storage capacity86of the washcoat36of the substrate34of the SCRF26. Yet another one of the inputs that can be utilized is a NOx flow rate88through the SCRF26. In other words, the flow rate of NOx gases through the SCRF26. Yet another one of the inputs that can be utilized is the amount of ash accumulated90inside the SCRF26. One or more of these inputs can be utilized by the controller42to determine or obtain the initial NOx conversion efficiency80. Therefore, one or more of these inputs can be utilized by a NOx map92to output the initial NOx conversion efficiency80. The NOx map92can use data obtained either through empirical testing or through analytic formulation. As such, for the NOx model60, obtaining1002the initial calculated efficiency68of the SCRF26can include determining one or more of the inputs discussed for this model60. Furthermore, in the embodiment ofFIG. 3, calculating1008the updated efficiency value74of the SCRF26can include calculating, via the controller42, the updated efficiency value74by multiplying the soot correction factor72with the initial NOx conversion efficiency80to update the efficiency of the NOx conversion. Simply stated, the initial NOx conversion efficiency80is multiplied (box93) by the soot correction factor72to equal (box95) the updated efficiency value74for the NOx conversion.

Referring toFIG. 4, for the absorption model62, the initial calculated efficiency68is further defined as an initial reductant absorption efficiency94representing the ability to absorb the reductant30on the substrate34of the SCRF26regarding the reductant absorption. For example, various inputs can be utilized to obtain the initial calculated efficiency68of the reductant absorption. One of the inputs that can be utilized is the temperature58of the substrate34of the SCRF26. Another one of the inputs that can be utilized is the exhaust flow rate82through the SCRF26. In other words, the flow rate of the exhaust gas stream14through the SCRF26. Yet another one of the inputs that can be utilized is the amount of reductant stored84on the washcoat36of the substrate34of the SCRF26. Yet another one of the inputs that can be utilized is an injection rate96of the reductant30into the exhaust stream14. Yet another one of the inputs that can be utilized is the amount of ash accumulated90inside the SCRF26. One or more of these inputs can be utilized by the controller42to determine or obtain the initial reductant absorption efficiency94. Therefore, one or more of these inputs can be utilized by an absorption map98to output the initial reductant absorption efficiency94. The absorption map98can use data obtained either through empirical testing or through analytic formulation. As such, for the absorption model62, obtaining1002the initial calculated efficiency68of the SCRF26can include determining one or more of the inputs discussed for this model62. Furthermore, in the embodiment ofFIG. 4, calculating1008the updated efficiency value74of the SCRF26can include calculating, via the controller42, the updated efficiency value74by multiplying the soot correction factor72with the initial reductant absorption efficiency94to update the efficiency of the reductant absorption. Simply stated, the initial reductant absorption efficiency94is multiplied (box97) by the soot correction factor72to equal (box99) the updated efficiency value74for the reductant absorption.

Referring toFIG. 5, for the desorption model64, the initial calculated efficiency68is further defined as an initial reductant desorption efficiency100representing an amount of the reductant30passing through the SCRF26regarding the reductant desorption. For example, various inputs can be utilized to obtain the initial calculated efficiency68of the reductant desorption. One of the inputs that can be utilized is the temperature58of the substrate34of the SCRF26. Another one of the inputs that can be utilized is the exhaust flow rate82through the SCRF26. In other words, the flow rate of the exhaust gas stream14through the SCRF26. Yet another one of the inputs that can be utilized is the amount of reductant stored84on the washcoat36of the substrate34of the SCRF26. Yet another one of the inputs that can be utilized is the injection rate96of the reductant30into the exhaust stream14. Yet another one of the inputs that can be utilized is the amount of ash accumulated90inside the SCRF26. One or more of these inputs can be utilized by the controller42to determine or obtain the initial reductant desorption efficiency100. Therefore, one or more of these inputs can be utilized by a desorption map102to output the initial reductant desorption efficiency100. The desorption map102can use data obtained either through empirical testing or through analytic formulation. As such, for the desorption model64, obtaining1002the initial calculated efficiency68of the SCRF26can include determining one or more of the inputs discussed for this model64. Furthermore, in the embodiment ofFIG. 5, calculating1008the updated efficiency value74of the SCRF26can include calculating, via the controller42, the updated efficiency value74by multiplying the soot correction factor72with the initial reductant desorption efficiency100to update the efficiency of the reductant desorption. Simply stated, the initial reductant desorption efficiency100is multiplied (box104) by the soot correction factor72to equal (box106) the updated efficiency value74for the reductant desorption.

Referring toFIG. 6, for the oxidation model66, the initial calculated efficiency68is further defined as an initial oxidation efficiency108representing the ability to oxidize the reductant30through the SCRF26regarding the reductant oxidation. For example, various inputs can be utilized to obtain the initial calculated efficiency68of the reductant oxidation. One of the inputs that can be utilized is the temperature58of the substrate34of the SCRF26. Another one of the inputs that can be utilized is the exhaust flow rate82through the SCRF26. In other words, the flow rate of the exhaust gas stream14through the SCRF26. Yet another one of the inputs that can be utilized is the amount of ash accumulated90inside the SCRF26. One or more of these inputs can be utilized by the controller42to determine or obtain the initial oxidation efficiency108. Therefore, one or more of these inputs can be utilized by an oxidation map110to output the initial oxidation efficiency108. The oxidation map110can use data obtained either through empirical testing or through analytic formulation. As such, for the oxidation model66, obtaining1002the initial calculated efficiency68of the SCRF26can include determining one or more of the inputs discussed for this model66. Furthermore, in the embodiment ofFIG. 6, calculating1008the updated efficiency value74of the SCRF26can include calculating, via the controller42, the updated efficiency value74by multiplying the soot correction factor72with the initial oxidation efficiency108to update the efficiency of the reductant oxidation. Simply stated, the initial oxidation efficiency108is multiplied (box112) by the soot correction factor72to equal (box114) the updated efficiency value74for the reductant oxidation.

The soot correction factor72can be a first numeric value of less than 1.0. Therefore, determining1004the soot mass estimate70can include selecting the first numeric value from the look-up table78. The look-up table78expresses the soot correction factor72as a function of the amount of soot inside the SCRF26. Generally, the soot correction factor72decreases as the amount of soot increases inside the SCRF26. After a thermal regeneration is performed to the SCRF26, generally, the amount of soot inside the SCRF26returns to approximately zero. As such, soot will again accumulate inside the SCRF26until the next thermal regeneration. This thermal regeneration cycle continues throughout the life of the vehicle10. Immediately before a thermal regeneration is performed, the first numeric value of the soot correction factor72is less than what the first numeric value of the soot correction factor72is immediately after a thermal regeneration is performed.

In one embodiment, the soot correction factor72has different numeric values for at least one of the NOx conversion, the reductant absorption, the reductant desorption and the reductant oxidation. The different numeric values for at least one of the NOx conversion, the reductant absorption, the reductant desorption and the reductant oxidation should be construed to include non-exclusive logical “or”, i.e., the NOx conversion or the reductant absorption or the reductant desorption or the reductant oxidation or combinations thereof. For example, the soot correction factor72can be a different value for each of the calculations to update the different efficiencies. In other words, the soot correction factor72can be a first value to update the efficiency for the NOx conversion, a second value different from the first value to update the efficiency for the reductant absorption, a third value different from the first and second values to update the efficiency for the reductant desorption and a fourth value different from the first, second and third values to update the efficiency for the reductant oxidation. As another example, the soot correction factor72can be the same value to update two of the efficiencies and different values to update the remaining two efficiencies. As yet another example, the soot correction factor72can be the same value to update three of the efficiencies and a different value to update the remaining one efficiency. In another embodiment, the soot correction factor72is the same numeric value to update each of the NOx conversion, the reductant absorption, the reductant desorption and the reductant oxidation.

It is to be appreciated that the order or sequence of performing the method1000as identified in the flowchart ofFIG. 2is for illustrative purposes and other orders or sequences are within the scope of the present disclosure. It is to also be appreciated that the method1000can include other features not specifically identified in the flowchart ofFIG. 2.

While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.