US20160153333A1 - CONVERSION OF NOx IN EXHAUST GAS - Google Patents
CONVERSION OF NOx IN EXHAUST GAS Download PDFInfo
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- US20160153333A1 US20160153333A1 US14/440,739 US201314440739A US2016153333A1 US 20160153333 A1 US20160153333 A1 US 20160153333A1 US 201314440739 A US201314440739 A US 201314440739A US 2016153333 A1 US2016153333 A1 US 2016153333A1
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- Prior art keywords
- nox
- exhaust
- ammonia
- scr catalyst
- data indicative
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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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
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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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/007—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
-
- 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
- F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
- F01N2550/05—Systems for adding substances into exhaust
-
- 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
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
-
- 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
- F01N2900/0601—Parameters used for exhaust control or diagnosing being estimated
-
- 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
- F01N2900/1402—Exhaust gas composition
-
- 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
- F01N2900/1622—Catalyst reducing agent absorption capacity or consumption amount
-
- 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
-
- 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
Definitions
- This disclosure relates generally to Selective Catalytic Reduction (SCR) of oxides of Nitrogen (NOx) in gaseous products of combustion, and more particularly to a system and method for estimating a quantity of ammonia (NH 3 ) consumed by SCR conversion of NOx in exhaust passing through an exhaust system of an internal combustion engine.
- SCR Selective Catalytic Reduction
- One engine exhaust technology for after-treatment of engine exhaust utilizes SCR to enable certain chemical reactions to occur between NOx and ammonia injected into an exhaust system. Those reactions convert NOx into Nitrogen (N 2 ) and water (H 2 O), two constituents found in abundance in earth's atmosphere. NOx and ammonia are the only reactants in certain of those reactions while Oxygen (O 2 ), which may be present in the exhaust, is a third reactant in other reactions.
- Ammonia is introduced in sufficient quantity to maintain a presence of ammonia on surfaces of the SCR catalyst where the chemical reactions to reduce NOx take place.
- a quantity of ammonia introduced into the exhaust system can be measured in various ways. However, that measurement doesn't necessarily equate to ammonia consumed to reduce NOx. If ammonia is being introduced in quantity which creates ammonia slip, some of the ammonia being introduced is not consumed and instead is exhausted into the atmosphere.
- the presently disclosed subject matter relates to estimating a quantity of ammonia actually consumed in reducing NOx to N 2 and H 2 O.
- One general aspect of the disclosed subject matter relates to an internal combustion engine comprising combustion chambers within which fuel is combusted to operate the engine, an intake system through which air for supporting combustion is introduced into the combustion chambers, an exhaust system through which exhaust resulting from combustion in the combustion chambers passes to atmosphere and which comprises an SCR catalyst, and an ammonia delivery system for introducing ammonia into the exhaust system upstream of the SCR catalyst for entrainment with exhaust flow toward the SCR catalyst.
- a processor processes certain data, including data indicative of a quantity of NOx in exhaust upstream of where ammonia is introduced into the exhaust system, data indicative of a quantity of NOx in exhaust downstream of the SCR catalyst, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed by chemical reactions which are enabled by the SCR catalyst to reduce NOx into N 2 and H 2 O.
- Another general aspect of the disclosed subject matter relates to a method for estimating a quantity of ammonia consumed by chemical reactions which are enabled by an SCR catalyst within an exhaust system of an internal combustion engine to reduce NOx in exhaust passing through the exhaust system to N 2 and H 2 O.
- the method comprises processing certain data, including data indicative of a quantity of NOx in exhaust upstream of where ammonia is being introduced into the exhaust system, data indicative of a quantity of NOx in exhaust downstream of the SCR catalyst, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed by chemical reactions which are enabled by the SCR catalyst within the exhaust system.
- the system comprises an SCR catalyst, an ammonia supply, an ammonia outlet through which ammonia from the ammonia supply is introduced into the exhaust flow, a downstream NOx sensor providing data indicative of a quantity of NOx in exhaust flow downstream of the SCR catalyst, a data source providing data indicative of a quantity of NOx in exhaust flow upstream of the ammonia outlet, and a processor for processing data from the downstream NOx sensor, data from the data source, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed to reduce NOx to N 2 and H 2 O by chemical reactions enabled by the SCR catalyst.
- SCR selective catalytic reduction
- FIG. 1 is a general schematic diagram of an internal combustion engine which utilizes SCR to reduce NOx in engine exhaust by chemical reaction with ammonia introduced into the exhaust.
- FIG. 2 is a diagram illustrating detail of a NOx reduction system present in FIG. 1 .
- FIG. 3 is a diagram of an algorithm for estimating a quantity of reductant (NH 3 ) consumed by chemical reaction with NOx in the NOx reduction system of FIG. 2 .
- FIG. 1 shows a representative internal combustion engine 10 which can be used in stationary or mobile applications.
- engine 10 may be a diesel engine which comprises structure forming a number of engine cylinders 12 into which fuel is injected by fuel injectors 14 to combust with air which has entered combustion chamber spaces of engine cylinders 12 through an intake system 16 when cylinder intake valves 18 for controlling admission of air from an intake manifold 20 into respective engine cylinders 12 are open.
- Engine 10 also comprises an exhaust system 22 through which engine exhaust created by combustion of injected fuel in the combustion chamber spaces to operate engine 10 is conveyed to atmosphere.
- Cylinder exhaust valves 24 control admission of exhaust from respective engine cylinders 12 into an exhaust manifold 26 for further conveyance through exhaust system 22 .
- Exhaust system 22 includes an exhaust after-treatment system 28 for treating exhaust prior to entry into the atmosphere.
- Other components which may be present in exhaust systems of contemporary diesel engines, such as a turbocharger turbine, are not shown.
- a processor-based engine control module (ECM) 30 controls various aspects of engine operation, such as fueling of engine cylinders 12 by fuel injectors 14 . Control is accomplished by processing various input data, indicated generally by reference numeral 32 , to develop control data for control of functions being performed by various devices.
- Exhaust after-treatment system 28 is shown in detail in FIG. 2 to comprise structure through which exhaust is constrained to pass.
- the particular structure shown comprises a generally cylindrical housing 34 having an axial length, an exhaust entrance 36 at an upstream axial end, and an exhaust exit 38 at a downstream axial end.
- Arrows 40 indicate a direction of exhaust flow into, through, and out of interior space of housing 34 .
- housing 34 contains a diesel oxidation catalyst (DOC) 42 downstream of exhaust entrance 36 and an SCR catalyst 44 downstream of DOC 42 .
- DOC 42 treats engine exhaust by removing certain entrained matter, such as the soluble organic fraction of diesel particulate matter.
- SCR catalyst 44 treats engine exhaust by reducing NOx according to chemical reactions such as:
- SCR catalyst 44 may be a type which not only reduces NOx but also traps entrained particulate matter (soot) and therefore requires occasional regeneration.
- An ammonia supply 46 stores ammonia which is used for NOx reduction
- Ammonia from supply 46 is introduced into the interior of housing 34 through a conduit 48 having an outlet 50 disposed at a location downstream of DOC 42 and upstream of SCR catalyst 44 .
- FIG. 2 is intended to portray good distribution of ammonia within the exhaust flow without reference to specific structural details of how that is accomplished so that a continuing presence of ammonia can be assured over as large a surface area of SCR catalyst 44 as possible.
- a processor-based ammonia dosing controller 52 controls the introduction of ammonia from ammonia supply 46 into housing 34 by processing various data, including data from ECM 30 with which it has communication. Controller 52 also processes data according to an algorithm for estimating a quantity of ammonia consumed by conversion of NOx in exhaust passing through exhaust system 22 . That algorithm 54 will be explained with reference to FIG. 3 .
- the algorithm processes data indicating a quantity of NOx as measured at a location upstream of outlet 50 and data indicating a quantity of NOx as measured at a location downstream of SCR catalyst 44 .
- These data are provided respectively by an upstream NOx sensor 56 upstream of DOC 42 and a downstream NOx sensor 58 , both shown in FIG. 2 .
- NOx sensor 58 is a type which also senses ammonia, and so the algorithm is premised on the assumption that ammonia is injected in quantity which causes minimal, nor no, slip.
- NOx sensor 56 may be replaced by a sufficiently accurate virtual NOx sensor.
- NOx sensor 56 may alternately be placed downstream of DOC 42 but upstream of ammonia outlet 50 .
- Controller 52 processes data from NOx sensor 56 indicating a quantity of NOx in untreated, i.e. “engine out”, exhaust and data from NOx sensor 58 indicating a quantity of NOx in exhaust which has been treated by SCR using ammonia stored on the surface of SCR 44 .
- the processing performs a first calculation 60 which yields a fraction equal to the quantity of NOx indicated by downstream NOx sensor 58 divided by the quantity of NOx indicated by upstream NOx sensor 56 .
- a second calculation 62 subtracts the calculated fraction from unity, leaving a resulting fraction representing the fraction of NOx which has been reduced.
- algorithm 54 uses the three chemical reactions given above and the result of calculation 62 to perform a calculation 64 of a quantity of ammonia which would have been consumed in order to reduce NOx to the resulting fraction calculated by step 62 . Because the NOx sensors do not distinguish between NO and NO 2 , the calculation may utilize a look-up table containing relative proportions of NO and NO 2 in the exhaust as a function of engine operation obtained by known techniques. The look-up table has been derived from previous mapping of engine exhaust at various engine operating conditions during engine development. Hence, algorithm 54 is repeatedly calculating the quantity of ammonia consumed to reduce NO and the quantity of ammonia consumed to reduce NO 2 over each interval of time between successive calculations as engine 10 operates.
- the calculation of the total quantity of ammonia consumed from an initial time to a present time is obtained by adding the respective quantities consumed to reduce NO and NO 2 during each interval between calculations. Because the calculation prior to a calculation 66 is based in parts per million (ppm), it must be converted from ppm to a flow rate [mass/time]. An estimate of the actual consumption is therefore calculated by calculation 66 which multiplies the result of calculation 64 by exhaust flow as measured or estimated in any suitably appropriate way. Depending on the unit of measurement of exhaust flow, a calculation 68 may be needed to convert the result of calculation 66 to desired units of ammonia consumption.
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- Chemical Kinetics & Catalysis (AREA)
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Abstract
Description
- This disclosure relates generally to Selective Catalytic Reduction (SCR) of oxides of Nitrogen (NOx) in gaseous products of combustion, and more particularly to a system and method for estimating a quantity of ammonia (NH3) consumed by SCR conversion of NOx in exhaust passing through an exhaust system of an internal combustion engine.
- One engine exhaust technology for after-treatment of engine exhaust utilizes SCR to enable certain chemical reactions to occur between NOx and ammonia injected into an exhaust system. Those reactions convert NOx into Nitrogen (N2) and water (H2O), two constituents found in abundance in earth's atmosphere. NOx and ammonia are the only reactants in certain of those reactions while Oxygen (O2), which may be present in the exhaust, is a third reactant in other reactions.
- Ammonia is introduced in sufficient quantity to maintain a presence of ammonia on surfaces of the SCR catalyst where the chemical reactions to reduce NOx take place.
- A quantity of ammonia introduced into the exhaust system can be measured in various ways. However, that measurement doesn't necessarily equate to ammonia consumed to reduce NOx. If ammonia is being introduced in quantity which creates ammonia slip, some of the ammonia being introduced is not consumed and instead is exhausted into the atmosphere.
- The presently disclosed subject matter relates to estimating a quantity of ammonia actually consumed in reducing NOx to N2 and H2O.
- One general aspect of the disclosed subject matter relates to an internal combustion engine comprising combustion chambers within which fuel is combusted to operate the engine, an intake system through which air for supporting combustion is introduced into the combustion chambers, an exhaust system through which exhaust resulting from combustion in the combustion chambers passes to atmosphere and which comprises an SCR catalyst, and an ammonia delivery system for introducing ammonia into the exhaust system upstream of the SCR catalyst for entrainment with exhaust flow toward the SCR catalyst.
- A processor processes certain data, including data indicative of a quantity of NOx in exhaust upstream of where ammonia is introduced into the exhaust system, data indicative of a quantity of NOx in exhaust downstream of the SCR catalyst, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed by chemical reactions which are enabled by the SCR catalyst to reduce NOx into N2 and H2O.
- Another general aspect of the disclosed subject matter relates to a method for estimating a quantity of ammonia consumed by chemical reactions which are enabled by an SCR catalyst within an exhaust system of an internal combustion engine to reduce NOx in exhaust passing through the exhaust system to N2 and H2O. The method comprises processing certain data, including data indicative of a quantity of NOx in exhaust upstream of where ammonia is being introduced into the exhaust system, data indicative of a quantity of NOx in exhaust downstream of the SCR catalyst, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed by chemical reactions which are enabled by the SCR catalyst within the exhaust system.
- Another general aspect of the disclosed subject matter relates to a system for estimating a quantity of ammonia consumed by selective catalytic reduction (SCR) for NOx reduction in exhaust flow through an exhaust after-treatment system. The system comprises an SCR catalyst, an ammonia supply, an ammonia outlet through which ammonia from the ammonia supply is introduced into the exhaust flow, a downstream NOx sensor providing data indicative of a quantity of NOx in exhaust flow downstream of the SCR catalyst, a data source providing data indicative of a quantity of NOx in exhaust flow upstream of the ammonia outlet, and a processor for processing data from the downstream NOx sensor, data from the data source, and data indicative of exhaust flow, in accordance with an algorithm to estimate a quantity of ammonia consumed to reduce NOx to N2 and H2O by chemical reactions enabled by the SCR catalyst.
- The foregoing summary is accompanied by further detail of the disclosure presented in the Detailed Description below with reference to the following drawings which are part of the disclosure.
-
FIG. 1 is a general schematic diagram of an internal combustion engine which utilizes SCR to reduce NOx in engine exhaust by chemical reaction with ammonia introduced into the exhaust. -
FIG. 2 is a diagram illustrating detail of a NOx reduction system present inFIG. 1 . -
FIG. 3 is a diagram of an algorithm for estimating a quantity of reductant (NH3) consumed by chemical reaction with NOx in the NOx reduction system ofFIG. 2 . -
FIG. 1 shows a representativeinternal combustion engine 10 which can be used in stationary or mobile applications. For example,engine 10 may be a diesel engine which comprises structure forming a number ofengine cylinders 12 into which fuel is injected byfuel injectors 14 to combust with air which has entered combustion chamber spaces ofengine cylinders 12 through anintake system 16 whencylinder intake valves 18 for controlling admission of air from anintake manifold 20 intorespective engine cylinders 12 are open. Other components which may be present in intake systems of contemporary diesel engines, such as a turbocharger compressor and charge air cooler, are not shown. -
Engine 10 also comprises anexhaust system 22 through which engine exhaust created by combustion of injected fuel in the combustion chamber spaces to operateengine 10 is conveyed to atmosphere.Cylinder exhaust valves 24 control admission of exhaust fromrespective engine cylinders 12 into anexhaust manifold 26 for further conveyance throughexhaust system 22. -
Exhaust system 22 includes an exhaust after-treatment system 28 for treating exhaust prior to entry into the atmosphere. Other components which may be present in exhaust systems of contemporary diesel engines, such as a turbocharger turbine, are not shown. - A processor-based engine control module (ECM) 30 controls various aspects of engine operation, such as fueling of
engine cylinders 12 byfuel injectors 14. Control is accomplished by processing various input data, indicated generally byreference numeral 32, to develop control data for control of functions being performed by various devices. - Exhaust after-
treatment system 28 is shown in detail inFIG. 2 to comprise structure through which exhaust is constrained to pass. The particular structure shown comprises a generallycylindrical housing 34 having an axial length, anexhaust entrance 36 at an upstream axial end, and anexhaust exit 38 at a downstream axial end.Arrows 40 indicate a direction of exhaust flow into, through, and out of interior space ofhousing 34. - Within its interior space,
housing 34 contains a diesel oxidation catalyst (DOC) 42 downstream ofexhaust entrance 36 and anSCR catalyst 44 downstream ofDOC 42. Exhaust which enters the interior space ofhousing 34 throughexhaust entrance 36 is forced to pass first throughDOC 42 and subsequently throughSCR catalyst 44 before exiting throughexhaust exit 38.DOC 42 treats engine exhaust by removing certain entrained matter, such as the soluble organic fraction of diesel particulate matter. SCRcatalyst 44 treats engine exhaust by reducing NOx according to chemical reactions such as: -
4NO+4NH3+O2→4N2+6H2O -
NO+NO2+2NH3→2N2+3H2O -
6NO2+8NH3→7N2+12H2O -
SCR catalyst 44 may be a type which not only reduces NOx but also traps entrained particulate matter (soot) and therefore requires occasional regeneration. - An
ammonia supply 46 stores ammonia which is used for NOx reduction Ammonia fromsupply 46 is introduced into the interior ofhousing 34 through aconduit 48 having anoutlet 50 disposed at a location downstream ofDOC 42 and upstream ofSCR catalyst 44.FIG. 2 is intended to portray good distribution of ammonia within the exhaust flow without reference to specific structural details of how that is accomplished so that a continuing presence of ammonia can be assured over as large a surface area ofSCR catalyst 44 as possible. - A processor-based
ammonia dosing controller 52 controls the introduction of ammonia fromammonia supply 46 intohousing 34 by processing various data, including data fromECM 30 with which it has communication.Controller 52 also processes data according to an algorithm for estimating a quantity of ammonia consumed by conversion of NOx in exhaust passing throughexhaust system 22. Thatalgorithm 54 will be explained with reference toFIG. 3 . - The algorithm processes data indicating a quantity of NOx as measured at a location upstream of
outlet 50 and data indicating a quantity of NOx as measured at a location downstream ofSCR catalyst 44. These data are provided respectively by anupstream NOx sensor 56 upstream ofDOC 42 and adownstream NOx sensor 58, both shown inFIG. 2 .NOx sensor 58 is a type which also senses ammonia, and so the algorithm is premised on the assumption that ammonia is injected in quantity which causes minimal, nor no, slip.NOx sensor 56 may be replaced by a sufficiently accurate virtual NOx sensor.NOx sensor 56 may alternately be placed downstream ofDOC 42 but upstream ofammonia outlet 50. -
Controller 52 processes data fromNOx sensor 56 indicating a quantity of NOx in untreated, i.e. “engine out”, exhaust and data fromNOx sensor 58 indicating a quantity of NOx in exhaust which has been treated by SCR using ammonia stored on the surface ofSCR 44. The processing performs afirst calculation 60 which yields a fraction equal to the quantity of NOx indicated bydownstream NOx sensor 58 divided by the quantity of NOx indicated byupstream NOx sensor 56. Asecond calculation 62 subtracts the calculated fraction from unity, leaving a resulting fraction representing the fraction of NOx which has been reduced. - Using the three chemical reactions given above and the result of
calculation 62,algorithm 54 performs acalculation 64 of a quantity of ammonia which would have been consumed in order to reduce NOx to the resulting fraction calculated bystep 62. Because the NOx sensors do not distinguish between NO and NO2, the calculation may utilize a look-up table containing relative proportions of NO and NO2 in the exhaust as a function of engine operation obtained by known techniques. The look-up table has been derived from previous mapping of engine exhaust at various engine operating conditions during engine development. Hence,algorithm 54 is repeatedly calculating the quantity of ammonia consumed to reduce NO and the quantity of ammonia consumed to reduce NO2 over each interval of time between successive calculations asengine 10 operates. The calculation of the total quantity of ammonia consumed from an initial time to a present time is obtained by adding the respective quantities consumed to reduce NO and NO2 during each interval between calculations. Because the calculation prior to acalculation 66 is based in parts per million (ppm), it must be converted from ppm to a flow rate [mass/time]. An estimate of the actual consumption is therefore calculated bycalculation 66 which multiplies the result ofcalculation 64 by exhaust flow as measured or estimated in any suitably appropriate way. Depending on the unit of measurement of exhaust flow, acalculation 68 may be needed to convert the result ofcalculation 66 to desired units of ammonia consumption.
Claims (16)
4NO+4NH3+O2→4N2+6H2O
NO+NO2+2NH3→2N2+3H2O
6NO2+8NH3→7N2+12H2O.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US14/440,739 US20160153333A1 (en) | 2012-11-05 | 2013-07-16 | CONVERSION OF NOx IN EXHAUST GAS |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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US201261722338P | 2012-11-05 | 2012-11-05 | |
PCT/US2013/050616 WO2014070262A1 (en) | 2012-11-05 | 2013-07-16 | Conversion of nox in exhaust gas |
US14/440,739 US20160153333A1 (en) | 2012-11-05 | 2013-07-16 | CONVERSION OF NOx IN EXHAUST GAS |
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US20160153333A1 true US20160153333A1 (en) | 2016-06-02 |
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US14/440,739 Abandoned US20160153333A1 (en) | 2012-11-05 | 2013-07-16 | CONVERSION OF NOx IN EXHAUST GAS |
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WO (1) | WO2014070262A1 (en) |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US20100101215A1 (en) * | 2008-10-24 | 2010-04-29 | Ming-Cheng Wu | Exhaust gas treatment system and methods for operating the same |
US8096110B2 (en) * | 2008-11-19 | 2012-01-17 | GM Global Technology Operations LLC | Ammonia (NH3) storage control system and method at low nitrogen oxide (NOx) mass flow rates |
US8769928B2 (en) * | 2010-09-27 | 2014-07-08 | Caterpillar Inc. | Exhaust system having cross-sensitive sensor |
-
2013
- 2013-07-16 WO PCT/US2013/050616 patent/WO2014070262A1/en active Application Filing
- 2013-07-16 US US14/440,739 patent/US20160153333A1/en not_active Abandoned
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