DE102014209960B4 - Method and device for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine - Google Patents
Method and device for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine Download PDFInfo
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- DE102014209960B4 DE102014209960B4 DE102014209960.9A DE102014209960A DE102014209960B4 DE 102014209960 B4 DE102014209960 B4 DE 102014209960B4 DE 102014209960 A DE102014209960 A DE 102014209960A DE 102014209960 B4 DE102014209960 B4 DE 102014209960B4
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- 230000003197 catalytic effect Effects 0.000 title claims abstract description 107
- 238000000034 method Methods 0.000 title claims abstract description 21
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000007789 gas Substances 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000011248 coating agent Substances 0.000 claims abstract description 10
- 238000000576 coating method Methods 0.000 claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims abstract description 9
- 230000005494 condensation Effects 0.000 claims abstract description 9
- 238000009833 condensation Methods 0.000 claims abstract description 8
- 238000010531 catalytic reduction reaction Methods 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims abstract description 5
- 239000003054 catalyst Substances 0.000 claims description 33
- 238000011144 upstream manufacturing Methods 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 10
- 238000012544 monitoring process Methods 0.000 description 7
- 229910021529 ammonia Inorganic materials 0.000 description 5
- 238000013461 design Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 238000003795 desorption Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000003745 diagnosis Methods 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
- F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
- F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
- F01N9/005—Electrical control of exhaust gas treating apparatus using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
- F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
- F01N2550/02—Catalytic activity of catalytic converters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/14—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics having more than one sensor of one kind
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/04—Methods of control or diagnosing
- F01N2900/0416—Methods of control or diagnosing using the state of a sensor, e.g. of an exhaust gas sensor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
- F01N2900/1404—Exhaust gas temperature
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1602—Temperature of exhaust gas apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1628—Moisture amount in exhaust apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
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- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
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Abstract
Verfahren zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem eines Dieselmotors, wobei das Abgassystem einen Dieselpartikelfilter (13) und einen stromabwärts hiervon angeordneten SCR-Katalysator (15) zur selektiven katalytischen Reduktion von im dem SCR-Katalysator (15) zugeführten Abgas enthaltenen Stickoxiden aufweist, dadurch gekennzeichnet, dass das Verfahren folgende Schritte aufweist:Messen wenigstens eines Temperaturwertes (T2) an einer Position stromabwärts des SCR-Katalysators (15);Durchführen eines ersten Vergleichs des gemessenen Temperaturwertes (T2) mit einem ersten Referenzwert für die Temperatur stromabwärts des SCR-Katalysators (15), wobei der erste Referenzwert einen Betriebszustand des Abgassystems mit funktionsfähigem SCR-Katalysator (15) repräsentiert;Durchführen eines zweiten Vergleichs des gemessenen Temperaturwertes (T2) mit einem zweiten Referenzwert für die Temperatur stromabwärts des SCR-Katalysators (15), wobei der zweite Referenzwert einen Betriebszustand des Abgassystems mit fehlerhaftem SCR-Katalysator (15) repräsentiert; undBewerten der Funktionsfähigkeit des SCR-Katalysators (15) auf Basis der Ergebnisse des ersten und des zweiten Vergleichs;wobei der erste Referenzwert und der zweite Referenzwert modellgestützt ermittelt werden, wobei bei dieser modellgestützten Ermittlung der Einfluss einer durch eine an der Oberfläche des SCR-Katalysators (15) stattfindende Kondensation von im Abgas enthaltenem Wasserdampf bewirkten exothermen Reaktion auf die Temperatur stromabwärts des SCR-Katalysators (15) abgeschätzt wird;wobei bei der modellgestützten Ermittlung des ersten Referenzwertes eine auf dem SCR-Katalysator (15) vorhandene Washcoat-Beschichtung berücksichtigt wird, und wobei bei der modellgestützten Ermittlung des zweiten Referenzwertes keine Washcoat-Beschichtung auf dem SCR-Katalysator (15) berücksichtigt wird.Method for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine, the exhaust system comprising a diesel particle filter (13) and an SCR catalytic converter (15) arranged downstream thereof for the selective catalytic reduction of exhaust gas supplied in the SCR catalytic converter (15) Has nitrogen oxides, characterized in that the method comprises the following steps: measuring at least one temperature value (T2) at a position downstream of the SCR catalytic converter (15); performing a first comparison of the measured temperature value (T2) with a first reference value for the temperature downstream of the SCR catalytic converter (15), the first reference value representing an operating state of the exhaust system with a functional SCR catalytic converter (15); performing a second comparison of the measured temperature value (T2) with a second reference value for the temperature downstream of the SCR catalytic converter (15 ), the second reference value represents an operating state of the exhaust system with a faulty SCR catalytic converter (15); and evaluating the operability of the SCR catalytic converter (15) on the basis of the results of the first and the second comparison; the first reference value and the second reference value being ascertained in a model-based manner, the influence of one on the surface of the SCR catalytic converter being determined in this model-based determination (15) The condensation of water vapor contained in the exhaust gas and the exothermic reaction to the temperature downstream of the SCR catalytic converter (15) is estimated; a washcoat coating present on the SCR catalytic converter (15) is taken into account in the model-based determination of the first reference value , and no washcoat coating on the SCR catalytic converter (15) is taken into account in the model-based determination of the second reference value.
Description
Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem eines Dieselmotors.The invention relates to a method and a device for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine.
Insbesondere betrifft die Erfindung ein Verfahren zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators gemäß dem Oberbegriff des Patentanspruches 1 sowie eine Vorrichtung zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators gemäß dem Oberbegriff des Patentanspruches 7.In particular, the invention relates to a method for evaluating the functionality of an SCR catalytic converter according to the preamble of patent claim 1 and a device for evaluating the functionality of an SCR catalytic converter according to the preamble of patent claim 7.
Die Einführung von immer strengeren NOx-Grenzwerten hat zur Entwicklung diverser Abgasnachbehandlungstechnologien geführt, um eine Kontrolle der NOx-Emissionen (= Stickoxid-Emissionen) im Abgas eines Dieselmotors zu erzielen. Eine dieser Lösungen ist der sogenannte NOx-Speicherkatalysator, dessen Funktionsprinzip darauf beruht, Stickoxide (NOx) unter mageren Abgasbedingungen zunächst zu speichern und dann unter Einstellung eines fetten, reduzierenden Abgasgemischs in einer Regenerationsphase umzuwandeln. Eine zweite Technologie ist die selektive katalytische Reduktion in einem sogenannten SCR-Katalysator (SCR = „Selective Catalytic Reduction“ = „selektive katalytische Reduktion“), wobei am SCR-Katalysator mittels Ammoniak die im Abgas enthaltenen Stickoxide zu Stickstoff (N2) reduziert werden. Darüber hinaus ist der SCR-Katalysator dazu in der Lage, das z.B. stromaufwärts des SCR-Katalysators direkt dem Abgasstrom zugeführte Ammoniak bei niedrigen Abgastemperaturen zu speichern.The introduction of ever stricter NO x limit values has led to the development of various exhaust gas aftertreatment technologies in order to control the NO x emissions (= nitrogen oxide emissions) in the exhaust gas of a diesel engine. One of these solutions is the so-called NO x storage catalytic converter, the principle of which is based on first storing nitrogen oxides (NO x ) under lean exhaust gas conditions and then converting them into a regeneration phase by setting a rich, reducing exhaust gas mixture. A second technology is selective catalytic reduction in a so-called SCR catalytic converter (SCR = "Selective Catalytic Reduction" = "selective catalytic reduction"), whereby the nitrogen oxides contained in the exhaust gas are reduced to nitrogen (N 2 ) on the SCR catalytic converter using ammonia . In addition, the SCR catalytic converter is able to store the ammonia, for example upstream of the SCR catalytic converter, which is fed directly to the exhaust gas stream at low exhaust gas temperatures.
Im Falle der Verwendung eines SCR-Katalysators in motorferner bzw. bodenseitiger Bauweise im Abgassystem ist vorteilhafterweise die Alterung eines solchen SCR-Katalysators in der motorfernen Position relativ begrenzt, da der SCR-Katalysators dann relativ etwa zum NOx-Speicherkatalysator oder im Vergleich zu einem SDPF-System (umfassend einen SCR-Washcoat auf einem Dieselpartikelfiltersubstrat) seltener hohen Temperaturen aufgrund des heißen Abgasstromes ausgesetzt ist. Allerdings ist zur Einhaltung der Emissionsvorschriften eine Überwachung der Funktionsfähigkeit bzw. der Degradation des SCR-Katalysators erforderlich.In the case of using an SCR catalytic converter in the exhaust system that is remote from the engine or at the bottom, the aging of such an SCR catalytic converter in the position remote from the engine is advantageously relatively limited, since the SCR catalytic converter is then relative to the NO x storage catalytic converter or compared to one SDPF system (comprising an SCR washcoat on a diesel particulate filter substrate) is rarely exposed to high temperatures due to the hot exhaust gas flow. However, monitoring the functionality or degradation of the SCR catalytic converter is necessary to comply with the emission regulations.
Ein beispielhafter Anwendungsfall eines Abgassystems, in welchem die Überwachung eines SCR-Katalysators in motorferner bzw. bodenseitiger Bauweise zur Erfüllung der Emissionsvorschriften erforderlich ist, ist eine Anordnung mit einem NOx-Speicherkatalysator in motornaher Bauweise in Verbindung mit einem passiven SCR-Katalysator (auch als pSCR-Katalysator bezeichnet) in bodenseitiger bzw. motorferner Bauweise.
Im Anwendungsfall eines sogenannten SDPF (d.h. einem Dieselpartikelfilter-Substrat mit darauf befindlicher SCR-Washcoat-Beschichtung) führt das Vorhandensein eines SCR-Katalysators in motorferner bzw. bodenseitiger Bauweise stromabwärts des SDPF ebenfalls zu einer robusteren Erfüllung der Emissionsvorschriften sowie zu einer Reduzierung des Ammoniakschlupfes.
Herkömmliche Ansätze zur Erfassung bzw. zum Nachweis eines Ausfalls eines SCR-Katalysators basieren z. B. auf der thermischen Trägheit des SCR-Katalysators, wobei sich jedoch die Realisierung eines robusten Nachweisverhaltens in einer bordeigenen Diagnostik in der Praxis häufig als problematisch erweist.Conventional approaches for the detection or detection of a failure of an SCR catalyst are based, for. B. on the thermal inertia of the SCR catalyst, but the realization of a robust detection behavior in an on-board diagnostics often proves to be problematic in practice.
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Es ist eine Aufgabe der vorliegenden Erfindung, ein Verfahren und eine Vorrichtung zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem eines Dieselmotors bereitzustellen, welche eine robuste Unterscheidung zwischen einem Betriebszustand des Abgassystems mit funktionsfähigem SCR-Katalysator und einem Betriebszustand des Abgassystems mit fehlerhaftem SCR-Katalysator ermöglichen.It is an object of the present invention to provide a method and an apparatus for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine, which can make a robust distinction between an operating state of the exhaust system with a functional SCR catalytic converter and an operating state of the exhaust system with a faulty SCR Enable catalyst.
Diese Aufgabe wird durch das Verfahren gemäß den Merkmalen des unabhängigen Patentanspruchs 1 bzw. die Vorrichtung gemäß dem nebengeordneten Patentanspruch 7 gelöst.This object is achieved by the method according to the features of independent patent claim 1 and the device according to the independent patent claim 7.
Ein erfindungsgemäßes Verfahren zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem eines Dieselmotors, wobei das Abgassystem einen Dieselpartikelfilter und einen stromabwärts hiervon angeordneten SCR-Katalysator zur selektiven katalytischen Reduktion von im dem SCR-Katalysator zugeführten Abgas enthaltenen Stickoxiden aufweist, weist folgende Schritte auf:
- - Messen wenigstens eines Temperaturwertes an einer Position stromabwärts des SCR-Katalysators;
- - Durchführen eines ersten Vergleichs des gemessenen Temperaturwertes mit einem ersten Referenzwert, wobei der erste Referenzwert einen Betriebszustand des Abgassystems mit funktionsfähigem SCR-Katalysator repräsentiert;
- - Durchführen eines zweiten Vergleichs des gemessenen Temperaturwertes mit einem zweiten Referenzwert, wobei der zweite Referenzwert einen Betriebszustand des Abgassystems mit fehlerhaften SCR-Katalysator repräsentiert; und
- - Bewerten der Funktionsfähigkeit des SCR-Katalysators auf Basis der Ergebnisse des ersten und des zweiten Vergleichs;
- - wobei der erste Referenzwert und der zweite Referenzwert modellgestützt ermittelt werden, wobei bei dieser modellgestützten Ermittlung der Einfluss einer durch eine an der Oberfläche des SCR-Katalysators stattfindende Kondensation von im Abgas enthaltenem Wasserdampf bewirkten exothermen Reaktion auf die Temperatur stromabwärts des SCR-Katalysators abgeschätzt wird.
- Measuring at least one temperature value at a position downstream of the SCR catalytic converter;
- Performing a first comparison of the measured temperature value with a first reference value, the first reference value representing an operating state of the exhaust system with a functional SCR catalytic converter;
- Performing a second comparison of the measured temperature value with a second reference value, the second reference value representing an operating state of the exhaust system with a faulty SCR catalytic converter; and
- - evaluating the functionality of the SCR catalytic converter based on the results of the first and the second comparison;
- - The first reference value and the second reference value are determined with the aid of a model, with this model-based determination being used to estimate the influence of an exothermic reaction on the surface of the SCR catalytic converter caused by water vapor contained in the exhaust gas on the temperature downstream of the SCR catalytic converter .
Der vorliegenden Erfindung liegt insbesondere das Konzept zugrunde, zur Überwachung eines SCR-Katalysators die Tendenz der Washcoat-Beschichtung des SCR-Katalysators auszunutzen, während einer Kaltstartphase Wasserdampf aus dem Abgas zu adsorbieren, wobei auf diese Adsorption eine Desorption des Wassers in einer späteren Phase des Testzyklus folgt. Die Kondensation des Wasserdampfes aus dem Abgas an der kalten Katalysatoroberfläche führt zu einer ausgeprägten exothermen Reaktion, welche mit einer erhöhten Temperatur im Abgassystem (insbesondere stromabwärts des SCR-Katalysators) einhergeht. Dieser Umstand wird erfindungsgemäß ausgenutzt, um Aufschluss über den Betriebszustand des Abgassystems bzw. die Funktionsfähigkeit des SCR-Katalysators zu erhalten.The present invention is based in particular on the concept of utilizing the tendency of the washcoat coating of the SCR catalyst to monitor water vapor from the exhaust gas during a cold start phase, with this adsorption being a desorption of the water in a later phase of the Test cycle follows. The condensation of the water vapor from the exhaust gas on the cold catalyst surface leads to a pronounced exothermic reaction, which is associated with an increased temperature in the exhaust system (in particular downstream of the SCR catalyst). This fact is used according to the invention to obtain information about the operating state of the exhaust system and the functionality of the SCR catalytic converter.
Weiterhin wird erfindungsgemäß bei der modellgestützten Ermittlung des ersten Referenzwertes eine auf dem SCR-Katalysator vorhandene Washcoat-Beschichtung berücksichtigt.Furthermore, according to the invention, a washcoat coating present on the SCR catalytic converter is taken into account in the model-based determination of the first reference value.
Desweiteren wird erfindungsgemäß bei der modellgestützten Ermittlung des zweiten Referenzwertes keine Washcoat-Beschichtung auf dem SCR-Katalysator berücksichtigt.Furthermore, according to the invention, no washcoat coating on the SCR catalytic converter is taken into account in the model-based determination of the second reference value.
Gemäß einer Ausführungsform erfolgt die modellgestützte Ermittlung des ersten und des zweiten Referenzwertes auf Basis einer Abschätzung der Wasserdampfkonzentration im Abgas.According to one embodiment, the model-based determination of the first and the second reference value based on an estimate of the water vapor concentration in the exhaust gas.
Gemäß einer Ausführungsform werden bei der modellgestützten Ermittlung des ersten und des zweiten Referenzwertes jeweils die Rate der Wasserkondensation an dem SCR-Katalysator sowie die Wärmefreisetzung abgeschätzt.According to one embodiment, the rate of water condensation on the SCR catalytic converter and the heat release are each estimated in the model-based determination of the first and the second reference value.
Gemäß einer Ausführungsform umfasst der Schritt des Bewertens der Funktionsfähigkeit des SCR-Katalysators jeweils das Ermitteln der mittleren quadratischen Abweichung für den ersten und den zweiten Vergleich innerhalb eines vorgegebenen Zeitfensters.According to one embodiment, the step of evaluating the functionality of the SCR catalytic converter in each case comprises determining the mean square deviation for the first and the second comparison within a predetermined time window.
Gemäß einer Ausführungsform erfolgt das Messen des wenigstens einen Temperaturwertes unmittelbar nach einem Kaltstart des Dieselmotors.According to one embodiment, the at least one temperature value is measured immediately after a cold start of the diesel engine.
Gemäß einer Ausführungsform weist das erfindungsgemäße Verfahren ferner folgende Schritte auf: Messen wenigstens eines Temperaturwertes an einer Position stromaufwärts des SCR-Katalysators, wobei das Bewerten der Funktionsfähigkeit des SCR-Katalysators ferner unter Berücksichtigung dieses zweiten Temperaturwertes erfolgt.According to one embodiment, the method according to the invention also has the following steps: measuring at least one temperature value at a position upstream of the SCR catalytic converter, the functioning of the SCR catalytic converter also being assessed taking this second temperature value into account.
Die Erfindung betrifft weiter eine Vorrichtung zum Bewerten der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem eines Dieselmotors, wobei die Vorrichtung dazu konfiguriert ist, ein Verfahren mit den vorstehend beschriebenen Merkmalen auszuführen.The invention further relates to a device for evaluating the functionality of an SCR catalytic converter in an exhaust system of a diesel engine, the device being configured to carry out a method with the features described above.
Weitere Ausgestaltungen der Erfindung sind der Beschreibung sowie den Unteransprüchen zu entnehmen.Further refinements of the invention can be found in the description and the subclaims.
Die Erfindung wird nachstehend anhand bevorzugter Ausführungsformen unter Bezugnahme auf die beigefügten Abbildungen erläutert.The invention is explained below on the basis of preferred embodiments with reference to the attached figures.
Es zeigen:
-
1 eine schematische Darstellung des möglichen Aufbaus eines Abgassystems, in welchem die Erfindung realisierbar ist; -
2 ein Diagramm eines beispielhaften Temperaturverhaltens in einem erfindungsgemäßen Abgassystem für unterschiedliche Fahrzeuge zur Erläuterung des der Erfindung zugrundeliegenden Konzepts; und -
3-4 Diagramme zur Verdeutlichung der Vorteile einer Überwachung der Funktionsfähigkeit eines SCR-Katalysators in einem Abgassystem.
-
1 is a schematic representation of the possible structure of an exhaust system, in which the invention can be implemented; -
2nd a diagram of an exemplary temperature behavior in an exhaust system according to the invention for different vehicles to explain the concept on which the invention is based; and -
3-4 Diagrams to illustrate the advantages of monitoring the functionality of an SCR catalytic converter in an exhaust system.
Das erfindungsgemäße Konzept ermöglicht eine robuste Unterscheidung zwischen einem Betriebszustand des Abgassystems mit funktionsfähigem SCR-Katalysator
Gemäß der Erfindung wird zur Überwachung der Funktionsfähigkeit des SCR-Katalysators
Die vorstehend beschriebene Adsorption bzw. Kondensation des Wasserdampfes aus dem Abgas an der kalten Katalysatoroberfläche bewirkt eine exotherme Reaktion, die wiederum mit einer erhöhten Temperatur stromabwärts des SCR-Katalysators
Das vorstehend beschriebene Temperaturverhalten ist in
Gemäß der Erfindung kann die Unterscheidung zwischen dem Betriebszustand des Abgassystems mit funktionsfähigem SCR-Katalysator
Insbesondere kann hierbei eine Abschätzung der Wasserdampfkonzentration im Abgas basierend auf dem Luft-Kraftstoff-Verhältnis und anderen Parametern des Verbrennungsprozesses erfolgen. Dabei können der Sättigungspartialdruck am SCR-Katalysator
Claims (7)
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US10323561B2 (en) | 2017-04-19 | 2019-06-18 | GM Global Technology Operations LLC | Methods for monitoring and modelling thermal characteristics of oxidation catalyst devices |
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DE102018111788A1 (en) * | 2018-05-16 | 2019-11-21 | Volkswagen Aktiengesellschaft | Method for detecting the icing of a particulate filter, in particular an Ottopartikelfilters |
DE102019118490A1 (en) * | 2019-07-09 | 2021-01-14 | Bayerische Motoren Werke Aktiengesellschaft | Evaluating a catalytic converter for a motor vehicle |
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