DE102018120687A1 - EMISSION CONTROL SYSTEM OF AN EXHAUST SYSTEM FOR A COMBUSTION ENGINE - Google Patents

Abstract

An emissions control system includes a selective catalytic reduction device, an injector for injecting a reductant into the device, an NO sensor disposed downstream of the device, a controller, an iterative model, and a table. The controller is configured to perform short-term and long-term control by confirming at least one short-term criterion. After confirming, the controller calculates a normalized model error using the model and a signal received from the sensor and integrates the normalized model error. If the integrated normalized model error exceeds a threshold, the controller continues with the long term control. If a long-term criterion is met, a current long-term factor and the integrated normalized model error are applied to the table to determine a new long-term factor. The new long-term factor is multiplied by an activation time of the injector.

Description

INTRODUCTION

The present disclosure relates to exhaust systems for internal combustion engines, and more particularly to exhaust systems having an adaptive selective catalytic reduction (SCR) emission control system.

The exhaust gas emitted by an internal combustion engine, particularly a diesel engine, is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide ("CO"), unburned hydrocarbons ("HC") and nitrogen oxides ("NO _x "), and condensed phase materials ( Liquids and solids) containing particles ("PM"). Catalyst compositions, typically disposed on catalyst carriers or substrates, are provided in an engine exhaust system as part of an aftertreatment system to convert some or all of these exhaust constituents into non-regulated exhaust gas components.

Exhaust treatment systems typically include selective catalytic reduction (SCR) devices. A SCR device includes to reduce a disposed thereon SCR catalyst, the amount of NO _x in the exhaust gas a substrate. The typical exhaust gas treatment system also includes a reducing agent supply system that a reducing agent such as ammonia (NH3), urea (CO (NH2) 2 and injecting other reducing agents. The SCR device uses NH3 for the reduction of NO _x. For example, when the appropriate amount of NH3 under the appropriate conditions is supplied to the SCR device, the NH3 However, when the reduction reaction rate is too slow or if excess ammonia in the exhaust gas is present to react with the NO _x in the presence of the SCR catalyst to reduce NO _x emissions., For example, if ammonia is present in the exhaust gas, the NO _x conversion efficiency is lowered.

SUMMARY

An emission control system in accordance with a non-limiting embodiment of the present disclosure addresses the exhaust gases of an internal combustion engine. The system includes a selective catalytic reduction (SCR) apparatus which is suitable for reducing emissions, a reducing agent injector which is suitable for injecting a reducing agent into the SCR device, a downstream _NOx sensor disposed downstream of the SCR device, a controller, an iterative model and a look-up table. The controller includes a processor and an electronic storage medium. The iterative model and the lookup table are stored on the electronic storage medium. The processor is configured to perform a short and long term adaptive control by confirming at least one short term release criteria. After confirmation, the processor computes a normalized chemical model error using the iterative model and a downstream NO _x signal received from the downstream NO _x sensor. The processor then integrates the normalized chemical model error to produce an integrated normalized chemical model error, and confirms that the integrated normalized chemical model error exceeds an error threshold. The processor may then transition to long-term adaptive control and confirm that at least one criterion of long-term adaptability is met. A current long term adaptive factor and the integrated normalized chemical model error are then applied to the lookup table to determine a new long term adaptive factor. The new long-term adaptive factor is multiplied by an activation time of the reducing agent injector.

In addition to the above embodiment, the emission control system includes an upstream _NOx sensor that is disposed upstream of the reductant injector and the SCR device, wherein the processor is configured to receive an upstream NO _x signal from the upstream _NOx sensor for the standardized to calculate chemical model error.

Alternatively or additionally, the normalized chemical model error in the above embodiment is related to the difference between a model predicted NO _x level from the iterative model and an actual NO _x level from the downstream NO _x signal.

Alternatively or additionally, the normalized chemical model error in the above embodiment is normalized by size.

Alternatively or additionally included in the foregoing embodiment, the at least one short-term release criterion at least one normalized error which is greater than a first threshold, a NO _x gradient which is smaller than a second threshold, a reducing agent consumers, a greater than third threshold, a temperature greater than a fourth threshold and less than a fifth threshold, a temperature gradient that is less than a sixth threshold, a deviation of the reducing agent storage level that is less than one seventh threshold and a combustion mode.

Alternatively or additionally, the at least one long-term activation criteria included in the foregoing embodiment, at least one of the normalized error is larger than an eighth threshold value, the NO _x gradient is smaller than a ninth threshold value, the consumed reducing agent is larger than a tenth threshold value wherein the temperature is greater than an eleventh threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reductant storage deviation is less than a fourteenth threshold, and the combustion mode.

Alternatively or additionally, in the above embodiment, the at least one short-term release criterion is independent of the at least one long-term release criterion.

An emission control system for treating the exhaust gas of an internal combustion engine according to a further non-limiting embodiment includes a selective catalytic reduction (SCR) device, a first NO _x sensor and a controller. The controller is configured to perform short and long term adaptive control by comparing a first NO _x measurement of the first NO _x sensor with a predicted NO _x value based at least in part on an initial chemical model. In response to meeting short-term activation criteria, the controller calculates a normalized chemical model error, integrates the normalized chemical model error, and calculates a new long-term adaptive factor when the integrated normalized chemical model error exceeds a threshold.

In addition to the previous embodiment, the emissions control system includes a look-up table stored in the controller and configured to compare a current long-term adaptive factor with the integrated normalized chemical model error to calculate the new long-term adaptive factor.

Alternatively or additionally, in the previous embodiment, the normalized chemical model error is normalized to a delta between the first NO _x measurement and a predicted NO _x value based on the original chemical model, and normalized based on size.

Alternatively or in addition, located in the preceding embodiment, the first NO _x sensor downstream of the SCR device.

Alternatively or additionally, the emissions control system includes a second NO _x sensor in the previous embodiment wherein the normalized chemical model error on the chemical output model, the first NO _x measurement and an upstream _NOx measurement from the second _NOx sensor, which is positioned upstream of the SCR device, based and wherein the first NO _x sensor downstream of the SCR device disposed.

Alternatively or additionally, in the previous embodiment, the emissions control system includes a temperature sensor configured to send a temperature measurement to the controller, wherein the chemical output model is generated by the controller and based at least on the temperature measurement, the upstream NO _x measurement, and the first NO _x measurement takes place.

Alternatively or additionally, in the above embodiment, the activation criterion is a short-term activation criterion.

Alternatively or additionally, the short-term release criterion included in the preceding embodiment, at least a normalized error which is greater than a first threshold value, a NO _x gradient which is smaller than a second threshold, a reducing agent consumer which is greater than a third threshold value , a temperature that is greater than a fourth threshold and less than a fifth threshold, a temperature gradient that is less than a sixth threshold, a deviation of the reductant storage level that is less than a seventh threshold, and a combustion mode.

Alternatively or additionally, in the previous embodiment, the long-term adaptive factor determination is performed when a long-term adaptive enabling criterion is met.

In the alternative or in addition, in the previous embodiment, the criteria of long-term adaptability are independent of the short-term capability criteria.

Alternatively or additionally, the criterion of long-term adaptability includes in the previous embodiment, at least one of the normalized error is larger than an eighth threshold value, the NO _x gradient smaller than a ninth threshold value, the consumed reducing agent is larger than a tenth threshold value if the temperature is greater than an eleventh threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reductant Memory deviation is less than a fourteenth threshold and the combustion mode.

Alternatively or additionally, in the previous embodiment, the eighth threshold is greater than the first threshold.

Alternatively or additionally, the emission control system in the previous embodiment includes a reductant injector, wherein the new long-term adaptive factor is generally applied with an activation time of the reductant injector.

The above features and advantages as well as other features and functions of the disclosure will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.

list of figures

• 1 ist ein Schema eines Kraftfahrzeugs mit einem Verbrennungsmotor und einem Abgassystem gemäß einer oder mehreren Ausführungsformen;
• 2 ist ein Schema des Abgassystems einschließlich eines Emissionssteuerungssystems;
• 3 ist ein Schema einer SCR-Vorrichtung der Emissionssteuerung;
• 4 ist eine Nachschlagetabelle, die in einer Steuerung der SCR-Vorrichtung als Teil eines langfristigen adaptiven (LTA) Steuerungsmerkmals gespeichert und von dieser angewandt wird; und
• 5 ist ein Flussdiagramm eines Verfahrens für die adaptive SCR-Steuerung und den langfristigen adaptiven (LTA) Eintrag.

Other features, advantages and details appear, by way of example only, in the following detailed description of the detailed description, which refers to the following drawings:

• 1 FIG. 12 is a schematic of a motor vehicle having an internal combustion engine and an exhaust system according to one or more embodiments; FIG.
• 2 Figure 11 is a schematic of the exhaust system including an emissions control system;
• 3 Fig. 10 is a schematic of an emission control SCR device;
• 4 FIG. 12 is a look-up table stored in and used by a controller of the SCR device as part of a long-term adaptive control (LTA) control feature; FIG. and
• 5 Figure 4 is a flowchart of a method for adaptive SCR control and long-term adaptive (LTA) entry.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure in its applications or uses. It should be understood that in the drawings, like reference characters designate like or corresponding parts and features. The term "module" as used herein refers to a processing circuit that includes an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or grouped) and a memory containing one or more software or firmware programs combinational logic circuit and / or other suitable components that can provide the described functionality.

A motor vehicle according to one aspect of an exemplary embodiment is generally at 20 in FIG 1 specified. The car 20 is shown in the form of a small truck. It goes without saying that the motor vehicle 20 take various forms, including automobiles, commercial transport, ships and the like. The car 20 includes a bodywork 22 with a passenger compartment 24 , a passenger compartment 26 and a cargo area 28 ,

An internal combustion engine (ICE) system 30 of the motor vehicle 20 can an internal combustion engine 32 , an exhaust system 34 and a controller 36 include. The engine compartment 24 In general, the internal combustion engine 32 take up. Examples of internal combustion engines 32 include a diesel engine, a gasoline or heptane engine and others.

The motor 32 of the ICE system 30 may include a plurality of crankshaft mounted reciprocating pistons that may be operably attached to a drive system, such as a vehicle drive system, to drive a vehicle (eg, to deliver tractive torque to the drive system). For example, the ICE system 30 any type of engine configuration or application, including various vehicle applications (eg, automotive, marine, and the like), as well as various non-vehicle applications (eg, pumps, generators, and the like). While the ICE system may be described in a vehicle-related context (eg, torque-generating), other non-vehicle related applications are within the scope of this disclosure. Therefore, when referring to a vehicle, this disclosure should be construed as covering any application of an ICE system 30 applies.

In addition, the ICE system 30 in general, represent any device capable of producing an exhaust gas flow generally through the exhaust system 34 is directed and treated. The exhaust gas may include chemical species or mixtures of chemical species; in gaseous, liquid or solid form requiring treatment. In one example, the exhaust gas may generally include gaseous (eg, NO _x , O ₂ ), carbonaceous, and / or particulate species. An exhaust gas stream may be a mixture of one or more NO _x species, one or more liquid hydrocarbon species, and one or more solid-particle species (eg, ashes). It is also to be understood that the embodiments disclosed herein may be applicable to the treatment of effluent streams that do not include carbonaceous and / or particulate species. Exhaust particles are generally carbonaceous soot and other solid and / or liquid carbonaceous species that are relevant to the exhaust gases of internal combustion engines or within the exhaust system 34 form.

With reference to 2 can the exhaust system 34 of the ICE system 30 at least part of the controller 36 , an exhaust pipe 38 (ie, exhaust manifold and pipe) and an emissions control system 40 include. The exhaust conduit generally extends above and in fluid communication with the internal combustion engine 32 and a tailpipe 42 the exhaust pipe 38 at the rear of the vehicle body 22 can be arranged. The emissions control system 40 is fluid with the exhaust pipe 38 connected, so that through the line 38 flowing exhaust gas (see arrows 44 ) from the emissions control system 40 is treated to reduce emissions before passing through the tailpipe 42 is discharged into the environment. The emissions control system 40 also allows the control and monitoring of the storage of one or more nitrogen oxides (NO _x ) and / or treatment materials by the internal combustion engine 32 control exhaust emissions generated.

The emissions control system 40 may include an oxidation catalyst (OC) device 46, a selective catalytic reduction (SCR) device 48, particulate filter devices (not shown), and other exhaust treatment devices. The SCR arrangement 48 may be downstream of the OC device 46 in relation to the exhaust pipe 38 to be ordered.

The OC device 46 the emissions control system 40 may be one of various flow through oxidation catalyst devices known in the art. The OC device 46 may be a flow-through metal or ceramic monolith substrate 50 include. The substrate 50 may be packaged in a stainless steel canister or housing, via an inlet and an outlet in fluid communication with the exhaust conduit 38 features. The substrate 50 may include an oxidation catalyst compound disposed thereon. The oxidation catalyst compound may be applied as a washcoat and may contain platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable metal oxide catalysts and combinations thereof. The OC device 46 is useful for the treatment of unburned gaseous and non-volatile HC and CO that oxidize to form carbon dioxide and water. A washcoat layer includes a compositionally different layer of material disposed on the surface of the monolithic substrate 50 or an underlying washcoat layer is arranged. A catalyst may include one or more washcoat layers, and each washcoat layer may have unique chemical catalytic functions.

The SCR arrangement 48 the emissions control system 40 can be customized to fit that of the OC device 46 treated and / or from the internal combustion engine 32 outgoing exhaust 44 absorbs and the nitrogen oxide (NO _x ) in the exhaust gas 44 reduced. NO _x components may include N _y O _x species where y> 0 and x> 0. Non-limiting examples of NO _x may include NO, NO ₂ , N ₂ O, N ₂ O ₂ , N ₂ O ₃ , N ₂ O ₄ , and N ₂ O ₅ . In particular, the SCR arrangement 48 Convert NO _x to diatomic nitrogen (N ₂ ) and water.

The SCR arrangement 48 can be at least part of the controller 36 , an SCR device or a canister 52 , An upstream _NOx sensor 54, a downstream _NOx sensor 56, at least one temperature sensor 58 , at least one pressure sensor 60 , a reducing agent injector 62 and a reductant supply source 64 include. The SCR device 52 is in fluid communication with the exhaust pipe 44 for the treatment of the exhaust gas 44 , The _NOx sensor 54 may be located upstream of the SCR device 52 and downstream of the OC device 46 be arranged to eliminate NO _x components in the exhaust 44 before measuring the exhaust gas into the SCR device 52 entry. The _NOx sensor 56 may be located downstream of the SCR device 52 be arranged to eliminate NO _x components in the exhaust 44 after measuring the exhaust gas into the SCR device 52 occurred. The temperature sensor 58 may be upstream of the SCR device 52 and downstream of the reductant injector 62 be arranged for measuring the exhaust gas temperature. Although the SCR device 52 downstream of the OC device 46 It should be noted that the SCR device 52 upstream of the OC device 46 can be arranged.

The at least one pressure sensor 60 (eg, differential pressure sensor) may be used to determine the pressure differential across the SCR device 52 be adjusted. Although a single differential pressure sensor 60 It should be understood that a variety of pressure sensors may be used to determine the pressure differential of the SCR device 52 to investigate. For example, a first pressure sensor may be located at the inlet of the SCR device 52 may be arranged, and a second pressure sensor may at the outlet of the SCR device 52 be arranged. Accordingly, the difference between the pressure detected by the second pressure sensor and the pressure detected by the first pressure sensor may be the pressure difference across the SCR 52 Show. It should be noted that in other examples, the sensors have different, additional or fewer sensors than the sensors described 54 . 56 . 58 . 60 may include.

The reducing agent injector 62 the SCR arrangement 48 can generally be on the exhaust pipe 38 upstream of the SCR device 52 (ie, between the upstream NOx sensor 54 and the temperature sensor 58 ) and configured to provide a controlled amount of a reductant 66 in the exhaust stream 44 distributed. The reducing agent 66 becomes from the reduction source 64 stored and the injector 62 and may be in the form of a gas, a liquid or an aqueous solution (eg aqueous urea solution). The reducing agent 66 can with air in the injector 62 be mixed to assist the dispersion of the injected spray. The SCR device 52 can the reducing agent 66 use, for example, ammonia (NH ₃ ) to reduce the NO _x .

The SCR device 52 the SCR arrangement 48 can be a substrate 68 include. The substrate 68 may generally be a particulate filter (PF), such as a diesel particulate filter (DPF), coated with an SCR catalyst and capable of absorbing carbon and other particulates from the exhaust gas 44 to filter or intercept. The substrate 68 generally includes an inlet and an outlet in fluid communication with the exhaust conduit 38 , In another example, the substrate may be a flow through monolith substrate, which may generally be ceramic. Further examples of substrates 68 may be wound or packed fiber filters, open-celled foams, sintered metal fibers, and others. The emissions control system 40 can also perform a regeneration process involving the substrate 68 by regenerating the particles trapped in the filter substrate.

The catalyst-containing washcoat, which is on the substrate 68 is arranged (ie, a flow through the catalyst or a wall flow filter), NO _x components in the exhaust gas 44 to reduce. The catalyst-containing washcoat may contain a zeolite and one or more base metal components such as iron (Fe), cobalt (Co), copper (Cu), or vanadium (V), which may work efficiently to remove NOx constituents of the exhaust gas 44 in the presence of NH ₃ . In one or more examples, a turbulator (ie, a mixer, not shown) may also be located in the exhaust conduit 38 in close proximity to the injector 62 and / or the SCR device 52 be arranged to continue thorough mixing of the reducing agent 66 with the exhaust 44 and / or even distribution throughout the SCR device 52 to support. It is understood that the catalyst compositions for the SCR function and the NH3 oxidation function in discrete washcoat layers on the substrate 68 or, alternatively, the compositions for the SCR and NH ₃ oxidation functions in discrete longitudinal zones on the substrate 68 may be present.

The body of the substrate 68 For example, a ceramic brick, plate structure, or any other suitable structure, such as a monolithic honeycomb structure that includes several hundred to several thousand parallel flow cells per square inch, although other configurations are suitable. Each of the flow cells can be defined by a wall surface on which the SCR catalyst composition can be applied by a washcoat process. The body of the substrate 68 may be formed of a material that matches the temperatures and the chemical environment associated with the exhaust gas 44 connected, can withstand. Some specific examples of materials that may be used include ceramics such as extruded cordierite, α-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, sillimanite, petalite, or a heat and corrosion resistant Metal, like titanium or stainless steel. The substrate 68 For example, it may comprise a non-sulphating TiO ₂ material. The body of the substrate 68 may be a PF device, as explained below.

The SCR catalyst composition is generally a porous material with a large surface area which can operate efficiently to NO _x components in the exhaust gas 44 in the presence of a reducing agent 66 (eg, ammonia). In some embodiments, the zeolite may be a β-zeolite, a Y-zeolite, a ZM5 zeolite, or any other crystalline zeolite structure, such as a chabazite or a USY (ultrastable Y-type) zeolite. The zeolite may include chabazite or SSZ. Suitable SCR catalyst compositions may have high thermal structure stability, especially when in tandem with the substrate 68 are used as a particulate filter (PF) device or when they are integrated into the SCRF devices described below that are regenerated using high temperature soot combustion methods.

The SCR catalyst composition may optionally also comprise one or more basic metal oxides as promoters to further reduce SO ₃ formation and improve the service life of the catalyst To extend the catalyst. The one or more basic metal oxides, in some embodiments, may include WO ₃ , Al ₂ O ₃ , and MoO ₃ . In one embodiment, WO ₃ , Al ₂ O ₃ , and MoO _{3 may be used} in combination with V ₂ O ₅ .

The SCR catalyst (ie the substrate 68 ) generally uses the reducing agent 66 to reduce NO _x species (eg NO and NO ₂ ) into innocuous components. These ingredients include one or more species that are not NO _x species, diatomic nitrogen (N ₂ ), nitrogen-containing inert species, or species that are considered acceptable emissions. The reducing agent 66 may be ammonia (NH ₃ ), such as anhydrous ammonia or aqueous ammonia, or may be generated from a nitrogen and hydrogen rich substance such as urea (CO (NH ₂ ) ₂ ). Additionally or alternatively, the reducing agent 66 Any composition that is capable of reacting in the presence of the exhaust gas 44 and / or decompose heat or react to form ammonia. Equations (1) - (5) provide exemplary chemical reactions for NO _x reduction with ammonia: 6NO + 4NH ₃ → 5N ₂ + 6H ₂ O (1) 4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (2) 6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (3) 2NO ₂ + 4NH ₃ + O ₂ → 3N ₂ + 6H ₂ O (4) NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (5)

It should be understood that equations (1) - (5) are merely illustrative and are not intended to be the SCR device 52 to limit a particular NO _x reduction mechanism or mechanisms, nor to preclude the operation of other mechanisms. The SCR device 52 may be configured to perform one of the above NO _x reduction reactions, combinations of equations (1) to (5), NO _x reduction reactions, and other NO _x reduction reactions.

The reducing agent 66 can be diluted with water, where the heat (eg, from the exhaust) evaporates the water and ammonia becomes the SCR device 52 fed. Non-ammonia reductants may be used as desired as a complete or partial alternative to ammonia. In implementations where the reducing agent 66 Contains urea, the urea reacts with the exhaust gas 44 to produce ammonia, that of the SCR device 52 is supplied. The subsequent reaction ( 6 ) provides an exemplary chemical reaction of ammonia production by urea decomposition: CO (NH ₂ ) ₂ + H ₂ O → 2NH ₃ + CO ₂ (6)

It is understood that equation (6) is illustrative only, and is not intended to, the decomposition of urea or other reducing agent 66 to a single mechanism and to exclude the operation of other mechanisms.

The substrate 68 (ie the SCR catalyst) may be the reducing agent 66 for the interaction with the exhaust gas 44 to save. The SCR device 52 has a reducing agent capacity or an amount of reducing agent or a reducing agent derivative that can be stored. The amount of one within an SCR device 52 stored reducing agent 66 in proportion to the capacity of the substrate 68 The SCR device may be referred to as the "reductant load" of the SCR device and may be expressed as a percentage (%) load (eg, 90% reductant load). During operation of the SCR device 52 is injected reducing agent 66 in the SCR catalyst of the substrate 68 stored and consumed during reduction reactions with unwanted NOx species and must be replenished continuously. The exact determination of the amount of reducing agent to be injected 66 is crucial to keep exhaust emissions at an acceptable level. Insufficient amounts of reducing agent 66 in the SCR device 52 may result in undesirable NO _x species emissions, referred to as NO _x breakthrough, and from the exhaust gas outlet tube 42 can escape. Too high a content of reducing agent 66 that enters the SCR device 52 can be injected, can cause unwanted levels of reducing agent 66 through the SCR device 52 not be implemented or the SCR device 52 as unwanted reaction product, also referred to as reducing agent slip left. Reducing agent slip and NO _x breakthrough can also occur if the temperature of the SCR catalyst of the substrate 68 is below a "light-off temperature". The SCR dosing logic may be from the controller 36 to control the reductant dosing.

The control 36 can be used for electronic communication with aspects of the internal combustion engine 32 , the source of reduction 64 , the injector 62 , the sensors 54 . 56 . 58 . 60 and other components of the ICE system 30 be adjusted. The control 36 can be a processor 70 (eg a microprocessor) and an electronic storage medium 72 which may be computer readable and writable. In one embodiment can the controller 36 an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or a group processor) and a memory that executes one or more software or firmware programs, a combinatorial logic circuit and / or other suitable components that the provide described functionality.

In operation, the processor 70 the controller 36 in the storage medium 72 stored SCR dosing logic and can continue to NO _x signals (see arrows 74 . 76 in 2 ) from the respective NO _x sensors 54 . 56 receive and process on NO _x levels in the exhaust 44 and adjacent the respective sensor position along the exhaust pipe 38 clues. Likewise, the processor can 70 a temperature signal (see arrow 78 ) from the temperature sensor 58 and a pressure signal (see arrow 80 ) from the pressure sensor 60 receive and process.

A reductant dosing rate (eg grams per second) may be provided by the processor 70 by applying an SCR chemistry model 82 and processing a feedback signal (see arrow 84 ) from the reductant supply source 64 of the injector 62 be determined. In general, the SCR chemistry model supports 82 in combination with the feedback signal 84 and the upstream NOx signal 74 in the SCR device 52 stored amount of reducing agent 66 predict. The chemical SCR model 82 also says NO _x levels of exhaust gas 44 ahead of the SCR device 52 be delivered. The chemical SCR model 82 For example, it may be updatable over one or more process values over time. For example, the chemical SCR model 82 be updated by a short-term correction factor.

With reference to 3 is the exhaust 44 generally illustrated as by the SCR device 52 streaming. The control 36 measures the flow rate (F) of the gas volume and the concentration C of the gas. For example, this is determined by the tax system 40 an input flow rate (see arrow 86 ) of NO _x as FC _{NOx, in} , where F is the volume of the incoming gas 44 and C _{NOx, in} the inlet concentration of NOx in the inflowing exhaust gas 44 is. Similarly, an input flow (see arrow 88 ) FC _{NH3, in} the volume of the flow of NH ₃ (ie, a reducing agent) in the inflowing exhaust gas 44 Wherein C _NH3, is _in the inlet concentration of NH _3. Furthermore, the controller 36 by compensating the adsorption amount (see arrow 90 ) and the desorption amount (see arrow 92 ) And reacted on the catalyst surface amounts _NH3 C determined as SCR concentration of NH ₃ and _NOx as SCR C-concentration of NO _x. Accordingly, FC _{NOx is} the NOx outlet volume flow rate (see arrow 94 ) NO _x through the outlet of the SCR device 52 , In one or more examples, the controller may 36 W _{NOx NOx} FC _x identify as the mass flow rate of NO, where W is the molecular weight of _NOx is NO _x. Similarly, the outlet volume flow rate (see arrow 96 ) for NH3 FC _NH3 , where the mass flow rate of NH3 is W _NH3 FC _NH3 .

Referring again to 2 controls the controller 36 the operation of the injector 62 based on the chemical model 82 and the desired reductant storage setpoint to an amount of reductant 66 to determine which is injected as described herein. The control 36 may be based on monitoring the one or more sensors 54 . 56 determine a long term factor (ie, a long term correction coefficient) corresponding to the reductant reservoir, and may be determined by the injector 62 more precisely control the amount of injected reducing agent provided. For example, the controller determines this 36 a reductant injector activation time, a long-term correction coefficient, a discrepancy between the chemical model 82 and the actual NO _x emissions at the outlet of the SCR device 52 continue to reduce or eliminate. Alternatively or additionally, the controller determines 36 a reductive setpoint correction (ie, a short-term correction factor) to account for the discrepancy between the chemical model 82 and the actual NO _x emissions at the output of the SCR device 52 to reduce or eliminate. That is, the chemical model 82 can be updated by the short term correction factor, and the long term factor from a lookup table 100 (please refer 4 ) can go directly to the DEF injector control (ie the controller 36 ) be applied. Accordingly, the supply of reducing agent 66 be used more efficiently. The control 36 can be that of the SCR device 52 amount of reductant supplied to reduce the amount of reductant storage (ie, that of the substrate 68 stored amount).

In one or more examples, the percentage of NOx that is from the exhaust 44 is removed into the SCR device 52 occurs as a conversion efficiency of the SCR device 52 be designated. The control 36 can the conversion efficiency of the SCR device 52 based on the NOxin and NOx _out signals 74, 76 generated by the respective NOx sensors 54, 56. For example, the controller 36 the conversion efficiency of the SCR device 52 based on the following equation: SCR CATALYST eff = (NOx _in - NOx _out ) / NOx _in (7)

Reducing agents (eg, NH ₃ ) may also be caused by an increase in the temperature of the SCR catalyst. For example, NH _{3 may be} from the SCR catalyst of the substrate 68 desorb as the temperature increases when the NH3 storage level is close to the maximum NH3 storage level. NH3 slip may also be due to an error (eg, memory level estimation error) or a faulty component (eg, faulty injector) in the emissions control system 34 occur.

Typically, the controller appreciates 36 an NH3 storage level of the SCR catalyst device 52 based on the chemical model 82 , In one or more examples, the NH ₃ storage set point ("set point") can be calibrated. That is, the NH3 storage setpoint may be a function of exhaust gas flow rate and temperature. Based on the current exhaust flow and the temperature, the setpoint can be defined.

The control 36 uses the chemical model 82 to estimate the current 3-level in the SCR device 52 and a reservoir level controller sends feedback to the injection controller to determine the amount of injection to provide NH3 for chemical model responses 82 and to determine a desired memory level. The set point may be a setpoint storage value for given operating conditions (eg, a temperature of the SCR catalyst of the substrate 68 ) specify. Accordingly, the target value may be a storage level (S) and a temperature (T) of the SCR device 52 show, see 3 , The setpoint can be referred to as (S, T). The control 36 controls the reducing agent injector 62 to reduce the amount of reducing agent in the exhaust 44 is injected to manage the memory level of the SCR device 52 to set to the setpoint. For example, the controller points 36 the injector 62 to increase or decrease the memory level to reach the setpoint when a new setpoint is detected. In addition, the controller indicates 36 the reducing agent injector 62 to increase or decrease the memory level to maintain the setpoint when the setpoint has been reached.

In one or more examples, the controller uses 36 the chemical model 82 of the SCR catalyst of the substrate 68 to the NOx concentration in the exhaust gases 44 placed in the SCR device 52 enter, predict. Furthermore, the controller determines 36 based on the predicted _NOx concentration an amount of NH3, with the exhaust gases 44 are to be dosed in order to meet the emission threshold. The control 36 typically implements an adaptive half-closed loop control strategy to maintain the performance of the SCR device 52 according to the chemical model 82 wherein the controller continuously learns one or more parameters corresponding to the chemical model 82 according to the current performance of the engine are assigned vehicle 20 ,

In one or more examples, the predetermined value may be determined based on a predetermined statistic, such as a standard deviation, for example, 1.5 standard deviation. Thus, the predetermined value may be further calibrated to a modeled downstream NO _x value. The measured downstream NO _x thus becomes against the expected error of the downstream NO _x sensor 56 normalized. The normalized error, 1.5 in this example, can then be compared to the threshold for entry into the steady state slip detection logic. The predetermined value of the concentration of the NO _x , which is used as the comparison threshold in this case, is calculated based on the earlier values of the NO _x measured by the NO _x sensor 56. In other words, in the above scenario, 37.5 ppm is used as the threshold since 37.5 is the 1.5 standard deviation value of previous NO _x measurements. It should be noted that in one or more examples, the NO _x measurement and the predicted value may be a NO _x flow rate or other NO _x attribute (instead of the NO _x concentration).

A dosing regulator (not shown) may be controlled by the controller 36 be controlled and configured to the chemical SCR model 82 generally predicted reductant storage levels (ie, in the substrate 68 the SCR device 52 ) and compares the predicted reductant storage level to a pre-programmed, desired reductant storage level. Deviations between the predicted reductant storage level and the desired reductant storage level may be continuously monitored and a dosing adjustment may be initiated (ie, both the short term correction factor and the long term factor) to increase or decrease the reductant dosing to eliminate the drift or reduce.

So the Reduktionsmitteldosierrate for example, can be adjusted to a desired NO _x concentration or flow rate in the exhaust gas 44 downstream of the SCR device 52 or to achieve a desired NO _x conversion rate. A desired conversion rate may be determined by many factors, such as the characteristics of the SCR catalyst type and / or the operating conditions of the ICE system 30 (eg engine 32 Operating parameters). To achieve optimal reductant dosing, the short-term correction factor can be applied to the chemical SCR model 82 generally representing the modeled NH3 storage. If the modeled and the desired memory differ, the dosage is changed to achieve the desired memory. That is, the long-term factor can be applied directly to the activation time of the injector and can increase or decrease the dosage accordingly. The short-term correction can be applied immediately, but the long-term correction will be made after a certain time.

Over time, inaccuracies of the chemical SCR model can increase 82 lead to appreciable errors between the modeled SCR reductant load and the actual load. Accordingly, the chemical SCR model 82 be continuously corrected to minimize or eliminate errors. A method for correcting a chemical SCR model 82 involves comparing the modeled SCR delivery gas NO _x levels with the actual NO _x levels (eg, as measured by the downstream NO _x sensor 56 ) to determine a discrepancy and then the chemical SCR model 82 to correct or reduce the discrepancy. Because the downstream NO _x sensor 56 towards the reducing agent 66 and the exhaust gas NO _x can be cross-sensitive, it is important to distinguish between reduction measurements and NO _x measurements, since otherwise an insufficient NO _x conversion is possible.

A passive analysis technique can be used to distinguish between reductive measurements and NO _x measurements, which is a correlation technique that involves comparing the NO _x concentration measured by the upstream NO _x sensor 54 , with the NO _x concentration measured by the downstream NO _x sensor 56 , includes. If the difference in concentration shows a divergent trend (ie, an increasing difference), this may indicate an increase or decrease in the reductant slip. The correlation analysis detects when the measurements of the downstream NO _x sensor 56 the pattern of the measurements of the upstream _NOx sensor 54 follow (ie the two sensor measurements are the same). The correlation is a statistical measure of the strength and direction of a linear relationship between the two NO _x sensors 54 . 56 ,

The comparison includes, for example, a correlation method wherein the downstream NO _x concentration is compared with the upstream NO _x measurements or the predicted NO _x measurements, wherein divergent concentration directions may indicate an increase or decrease in reductant slip. For example, if the upstream NO _x concentration decreases and the downstream NO _x concentration increases, the reductant slip may be identified as increasing. Similarly, as the upstream NO _x concentration increases and the downstream NO _x concentration decreases, the reductant slip may be identified as decreasing. Thus, the deviation between the two sequences of NO _x measurements can be used to determine a dosing status of the SCR device 52 to determine.

Alternatively or additionally, the comparison includes a frequency analysis. NO _x signals 74 . 76 that are from NO _x sensors 54 . 56 Because of the variation in NO _x and reductant concentrations during modulation / demodulation, they may contain multiple frequency components (eg, high frequency and low frequency). High frequency signals generally refer only to the NO _x concentration, while low frequency signals generally relate to both the NO _x concentration and the reducing agent concentration. High-frequency signals for the upstream and the downstream NO _x NO _x be isolated and used to compute an SCR NO _x conversion ratio, which is then applied to the isolated upstream _NOx measurement to a low downstream _NOx measurement to determine. The calculated low frequency downstream NO _x measurement is then compared to the actual isolated low frequency downstream NO _x measurement, wherein a deviation between the two values may indicate a reductant slip.

A disadvantage of passive analysis techniques (ie, short-term techniques) such as the correlation method and frequency method described above is that they rely on the proper operation of two NO _x sensors 54 . 56 based. For example, a faulty upstream _NOx sensor 54 a NO _x signal 74 which is lower than the actual NO _x level near the upstream NO _x sensor, which causes the SCR chemical model 82 predicts a higher reductant storage than the actual storage. Accordingly, the NO _x breakthrough would be erroneously identified as reductant slip, and the dosage of reductant would be controlled so that the NO _x breakthrough would worsen (ie reducing reductant dosage would be reduced). Furthermore, the chemical SCR model would 82 be updated using the inaccurate upstream NO _x measurement and the increased NO _x breakthrough would persist. Additionally or Alternatively, similarly, a reductant slip may be misinterpreted as NO _x breakthrough.

In general, passive analysis or short term techniques can be used to partially predict the presence of NH3 slip and / or NOx breakthrough. However, the mere application of the short-term techniques does not compensate for the system drift, part-to-part fluctuations, and other factors, thereby making false slip decisions that result in incorrect short-term memory level corrections. Incorrect short term memory level corrections can lead to wrong long term adjustment decisions. That is, if there is a system drift problem, the mere application of a short-term technique may cause saturation of NH3 slip and / or NO _x breakthrough predictions. The emissions control system 40 therefore applies both a short-term and a long-term correction. More specifically, a long-term adjustment that depends only on accumulated errors.

Based on BILD 4 can in the electronic storage medium 72 the controller 36 (please refer 1 ) a card or lookup table 100 stored in the execution of a long-term adaptive control (LTA) by the processor 70 as part of the SCR arrangement 48 the emissions control system 34 , is used. Table 100 may include multiple rows of integrated, short-term normalized error categories or values, which include both NH3 slip error lines and NO _x breakthrough error lines. That is, the normalized error with respect to NH3 slip includes several values 102S (ie, rows) expressed as positive values, and the normalized NO _x breakthrough error includes multiple values 102B (ie lines). The numerous columns in the lookup table 100 are the current long-term adjustment factors 104 assigned. In operation, the processor references 70 the controller 36 the current long-term adjustment factor 104 on the integrated short-term standardized error 102 to a new long-term adjustment factor 106 to investigate.

With reference to 5 is a flowchart of a method 200 for adaptive SCR control and long-term adaptive (LTA) entry. The procedure 200 can through the control 36 and / or one or more circuits can be realized. The procedure 200 can be implemented by executing logic in the form of computer readable and / or executable instructions on the storage medium 72 the controller 36 can be provided or stored. At block 202 At least one short-term activation criterion is fulfilled. Examples of short-term activation criteria are: a normalized chemical model error is greater than a first threshold value, a NO _x gradient is smaller than a second threshold, a spent reducing agent (e.g. NH3.) Is greater than a third threshold value (eg. Stability of the SCR device), a temperature window (ie, a temperature is greater than a fourth threshold and less than a fifth threshold), a temperature gradient is less than a sixth threshold, a reductant storage level deviation is less than a seventh threshold, and a combustion mode.

The normalized chemical model error, which is greater than the first threshold, and as part of the short-term activation, can generally be the difference between the predicted NO _{x of} the chemical SCR model 82 and the actual NO _x , normalized by size. The NO _x gradient is less than a second threshold and, as part of the short-term activation, may have a rate of change (eg, ppm / s) of NO _x into the SCR device 52 be. A large gradient can be an indicator of a very volatile vehicle maneuver where corrections are desirable. The spent reducing agent (eg NH3) is generally a stability criterion for the SCR device 52 ,

The temperature window as part of the short term release is generally an indicator of a temperature that is higher than a low temperature threshold and lower than a high temperature threshold. The criteria of the temperature window may allow adaptation of the short-term correction to the work area in which the chemical model SCR 82 most accurate. That is, the chemical SCR model 82 at very low temperatures, where power is reduced, or at very high temperatures, where there is a tendency for NH3 slip, may not be as accurate.

The temperature gradient, which is less than the sixth threshold, is an indicator of a temperature change rate at the input of the SCR device as part of the short term release 52 , A large gradient can be an indicator of a very volatile vehicle maneuver, where no corrections are desirable.

The reductant storage level deviation is less than a seventh threshold and, in the context of the short-term release, allows adaptation of the short-term correction to the work area in which the chemical SCR model is located 82 most accurate. The chemical SCR model 82 may not be accurate if the actual reductant storage level at the SCR Catalyst is much higher or lower than the set point (ie the seventh threshold).

The criteria for the combustion mode allow the short-term correction to be disabled in the combustion mode (eg, DPF regeneration, SCR warm-up, and others). Certain combustion modes may be prone to increased temperatures, reduced storage capacity, and increased NH3 slip. Under such conditions, short-term corrections should be avoided.

At block 204 and if the short-term activation criteria are met, the controller can calculate the normalized chemical model error. Inputs to the normalized chemical model error are the signals 74 . 76 the respective upstream and downstream NO _x sensors 54 . 56 and the chemical SCR model 82 , The chemical SCR model 82 can be from the inputs of the temperature sensor 58 , the NO _x sensors 54 . 56 and the previous chemical SCR model 82 that in the controller 36 is included, formed and developed. The normalized chemical model error may be equal to the delta between the measured NO _x , that of the downstream NO _x signal 76 and the modeled or predicted downstream NO _x is normalized based on size of values.

At block 206 the normalized chemical model error associated with the short-term control is integrated. In one example, the task rate for this integration may be about fifty milliseconds. At block 208 can the procedure 200 if the integrated normalized chemical model error exceeds a threshold, proceed to a long-term adaptive factor determination. At block 210 and the continuation of the long-term adaptive factor determines whether the long-term adaptability criteria are met. The long-term adaptability criteria may be similar to the short-term adaptability criteria except that the respective thresholds may be different. That is, the thresholds between the long-term adjustment criteria may be independent of the short-term adjustment criteria. In general, all thresholds may depend on the SCR strategy and the hardware.

Examples of the criterion of long-term adaptability include: the normalized error greater than an eighth threshold, where the NO _x gradient is less than a ninth threshold, the consumed reducing agent (eg, NH3) is greater than a tenth threshold (ie stability of the SCR device) the temperature is greater than an eleventh threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reductant storage deviation is less than a fourteenth threshold (ie, a fourteenth threshold), and combustion mode.

In one embodiment, the normalized error threshold for the long term adjustment (i.e., the eighth threshold) may be substantially greater than the normalized error threshold for the short term correction (i.e., the first threshold). Furthermore, the various thresholds of the long-term adjustment criteria may be about twice as high as the respective thresholds of short-term adjustment criteria. In further embodiments, the thresholds may be approximately equivalent.

At block 212 and if the criteria for long-term adjustment are met, the integrated normalized chemical model error will be used 102 and the current long-term adaptive factor 104 as inputs to the map or the lookup table 100 used to create a new (ie subsequent) long-term adaptive factor 106 to determine. For example, if the integrated short-term normalized error 102 is about 0.3 (ie an integrated short-term normalized error related to NH3 slip) and the current long-term adjustment factor is about 0.8, the new long-term adjustment factor would be 106 about 0.77 (ie as an exemplary representation). The new long-term adjustment factor 106 can then be used to compensate for system drift and / or part-to-part variations. In one example, the new long-term adjustment factor 106 In general, multiply the activation time of the DEF injector (ie, the time that the injector remains open).

The technical solutions described herein facilitate improvements in emission control systems used in internal combustion engines, such as those used in vehicles. The technical solutions for example, determine the memory correction and adjustment due to the integration of a smaller error than that of the entry of a stationary reducing agent slip detection logic wherein the error indicating a difference between the measurement of the downstream _NOx sensor and the downstream NO _x model. Such improvements facilitate the prevention of the steady state reductant slip detection cycle when the NO _x error is just high enough to cause a stationary reductant slip detection event, but the error is low enough for the system to turn on and off the steady state Reducing agent slip detection without switching on and off.

Further advantages and benefits are a system 40 , which is configured for both short-term and long-term customization. This independence helps to improve adaptation robustness, reduce false losses, and reduce the potential for DEF crystallization.

While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and the individual parts may be substituted with corresponding other parts without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular material situation to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but include all embodiments that fall within its scope.

Claims (10)

An emissions control system for treating exhaust gas in an internal combustion engine, the emissions control system comprising: a selective catalytic reduction (SCR) device for reducing emissions; a reducing agent injector adapted to inject a reducing agent into the SCR device; a downstream NOx sensor disposed downstream of the SCR device; a controller having a processor and an electronic storage medium; an iterative model stored on the electronic storage medium; and a look-up table stored in the electronic storage medium, and wherein the processor is configured to perform short-term and long-term adaptive control by: confirming that at least one short-term activation criterion is met; Calculating a normalized model chemical error using the iterative model and a downstream NO _x signal received from the downstream NO _x sensor; Integrating the normalized chemical model error to produce an integrated normalized chemical model error; Confirming that the integrated normalized chemical model error exceeds an error threshold; Continuing in the direction of long-term adaptive control; Confirming that at least one long-term adaptation criterion has been met; Applying a current long term adjustment factor and the integrated normalized chemical model error to the lookup table to determine a new long term adjustment factor; and multiplying the new long-term adjustment factor by an activation time of the reducing agent injector. Emission control system according to Claim 1 Further comprising: receiving an upstream _NOx sensor disposed upstream of the reductant injector and the SCR device, wherein the processor is configured, an upstream NO _x signal from the upstream _NOx sensor for the standardized to calculate chemical model error. Emission control system according to Claim 1 wherein the normalized chemical model error is associated with the difference between a model predicted NO _x level from the iterative model and an actual NO _x level from the downstream NO _x signal. Emission control system according to Claim 3 in which the normalized chemical model error is normalized by size. Emission control system according to Claim 1 Wherein the at least includes at least a short-term release criterion a normalized error which is greater than a first threshold value, a NO _x gradient which is smaller than a second threshold, a reducing agent consumer that is greater than a third threshold, a temperature , which is greater than a fourth threshold and less than a fifth threshold, a temperature gradient that is less than a sixth threshold, a reducing agent storage level that is less than a seventh threshold, and a combustion mode. Emission control system according to Claim 5 Wherein the includes at least one of the normalized errors at least a long-term release criterion, which is greater than an eighth threshold value, the NO _x gradient smaller than a ninth threshold value, the consumed reducing agent is larger than a tenth threshold value, the temperature is greater than an eleventh Threshold and less than a twelfth threshold, the temperature gradient is less than a thirteenth threshold, the reducing agent storage deviation is less than a fourteenth threshold, and the combustion mode. Emission control system according to Claim 1 wherein the at least one short-term release criterion is independent of the at least one long-term release criterion. An emission control system for treating exhaust gas of an internal combustion engine, the emission control system comprising: a selective catalytic reduction (SCR) device; a first NO _x sensor; and a controller configured to perform short and long-term adaptive control by: comparing a first NO _x measurement from the first NO _x sensor with a predicted NO _x value based at least in part on an initial chemical model, and in response to meeting short-term activation criteria: calculating a normalized chemical model error; Integrating the normalized chemical model error; and calculating a new long-term adaptive factor when the integrated normalized chemical model error exceeds a threshold. Emission control system according to Claim 8 , further comprising: a lookup table stored in the controller and configured to compare a current long term adaptive factor with the integrated normalized chemical model error to calculate the new long term adaptive factor. Emission control system according to Claim 9 wherein the normalized chemical model error equals a delta between the first NO _x measurement and a predicted NO _x value based on the original chemical model, and normalizes based on the size.

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