WO2004016917A1 - Reduction des emissions pour moteur a combustion interne - Google Patents

Reduction des emissions pour moteur a combustion interne Download PDF

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Publication number
WO2004016917A1
WO2004016917A1 PCT/AU2003/001035 AU0301035W WO2004016917A1 WO 2004016917 A1 WO2004016917 A1 WO 2004016917A1 AU 0301035 W AU0301035 W AU 0301035W WO 2004016917 A1 WO2004016917 A1 WO 2004016917A1
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WO
WIPO (PCT)
Prior art keywords
engine
internal combustion
catalyst
exhaust
approximately
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Application number
PCT/AU2003/001035
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English (en)
Inventor
Koon Chul Yang
Original Assignee
Orbital Engine Company (Australia) Pty Limited
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Filing date
Publication date
Application filed by Orbital Engine Company (Australia) Pty Limited filed Critical Orbital Engine Company (Australia) Pty Limited
Priority to AU2003249788A priority Critical patent/AU2003249788A1/en
Publication of WO2004016917A1 publication Critical patent/WO2004016917A1/fr

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Classifications

    • 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
    • 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
    • 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
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/0255—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus to accelerate the warming-up of the exhaust gas treating apparatus at engine start
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M27/00—Apparatus for treating combustion-air, fuel, or fuel-air mixture, by catalysts, electric means, magnetism, rays, sound waves, or the like
    • F02M27/02—Apparatus for treating combustion-air, fuel, or fuel-air mixture, by catalysts, electric means, magnetism, rays, sound waves, or the like by catalysts
    • 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

Definitions

  • This invention relates to internal combustion engines and emissions standards for internal combustion engines, and more particularly to the calibration, control and operation of direct injection engines and lean bum stratified charge engines so as to comply with certain emissions standards.
  • Such direct injection (Dl) engine technologies are considered by some to be the next evolutionary step for internal combustion engines and examples of automotive vehicles incorporating Dl engines are in fact already available to the consumer in various automotive markets.
  • These commercially available models typically utilise a single fluid direct injection fuel system which injects fuel at high pressure directly into the combustion chambers of the engine. High fuel pressures are used to assist with the better atomization of the fuel as it is delivered into the engine combustion chambers.
  • the ULEV II and SULEV emissions requirements are particularly stringent standards, with SULEV being more stringent than ULEV II.
  • MPI and Dl engines include one or more catalytic converters or an exhaust gas after treatment system of some nature located in the exhaust system of the vehicle.
  • Catalytic converters typically act to convert undesirable exhaust emissions such as hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) into substances such as carbon dioxide, nitrogen, oxygen and water. This is effected by certain chemical conversion processes that take place within the catalytic converter and typically include oxidation reactions and reduction reactions.
  • a catalyst normally requires to be operated in a certain temperature range.
  • the temperature of a catalyst is such that is able to convert raw engine exhaust emissions (eg. CO or HC) with 50% conversion efficiency, the catalyst is said to have attained a light-off state or condition (ie. "light-off").
  • the time delay from engine start to attaining this necessary temperature level can be referred to as the "light-off time”.
  • catalyst size is also an important issue that needs to be addressed when seeking to provide an economically viable engine exhaust after treatment system. This is predominantly due to the fact that catalysts typically utilise precious metals such as platinum and rhodium. Accordingly, catalyst cost is largely dictated by the amount of precious metal that is contained therein. Hence, it is preferable to use smaller catalysts where possible.
  • an internal combustion engine including one or more combustion chambers, an exhaust system coupled to the engine for enabling the egress of exhaust combustion gases from the or each combustion chamber, and an electronic control unit (ECU) for controlling operation of the engine, wherein the exhaust system comprises at least an oxidation catalyst and wherein the ECU is adapted to control the engine whereby the temperature of the exhaust combustion gases fed into the exhaust system exceeds 400°C within approximately five seconds of starting said engine.
  • ECU electronice control unit
  • the temperature of the catalyst exceeds approximately 300°C within approximately ten seconds of engine operation. That is, the rapid increase in the temperature of the exhaust combustion gases within a very short time following engine starting contributes directly to reducing the light-off time for the oxidation catalyst in the exhaust system.
  • the exhaust feed gas temperature exceeds approximately 500°C within approximately five seconds of engine starting.
  • the exhaust feed gas temperature exceeds approximately 700°C within approximately 10 seconds of operation from starting.
  • the exhaust feed gas temperature conveniently peaks at between 750°C and 800°C within approximately 15 seconds of engine operation.
  • ECU control of the engine results in pre-catalyst engine out cumulative hydrocarbon emissions being less than approximately 0.09 grams after ten seconds of engine operation.
  • This figure of 0.09 grams is derived from a maximum of 50% of the total SULEV NMOG emission mass permitted over a single FTP drive cycle (when taking into account the FTP weighted factor) and is typically used as a threshold target for the amount of total HC emissions permitted to be generated by an engine before the catalyst in the exhaust system has attained the light-off condition.
  • pre-catalyst engine out cumulative hydrocarbon emissions are less than approximately 0.06 grams after ten seconds of engine operation. Conveniently, the pre-catalyst engine out cumulative hydrocarbon emissions are less than approximately 0.12 grams after twenty seconds of engine operation. Preferably, the pre-catalyst engine out cumulative hydrocarbon emissions produced by the engine facilitate the engine satisfying the SULEV or ULEV II legislated NMOG requirements.
  • the SULEV and ULEV II emissions requirements are based on testing of a vehicle (and hence an engine) over an FTP drive cycle which effectively sets out certain predefined engine operating conditions.
  • the FTP drive cycle requires engine operation from a cold start and that there be an initial period of idle operation before any driver load is placed on the engine.
  • the engine under control of the ECU, undergoes a cold start.
  • the temperature of the exhaust combustion gases fed into the exhaust system is controlled by the ECU to exceed 400°C within approximately five seconds of engine starting and whilst the engine is operating at idle.
  • the engine is operated at near full load fuelling levels and with a spark timing set to after top dead center during at least a portion of the first twenty seconds of engine operation.
  • a spark timing is set within the order of 20° to 30° after top dead center.
  • the torque output of the engine is reduced to that which would be expected during typical idle operation.
  • the catalyst arranged in the exhaust system preferably has a volume less than
  • the volume of the catalyst is less than 85% of the engine swept volume. In certain applications, the volume of the
  • ⁇ catalyst is in the range of 50% to 60% of the engine swept volume.
  • the engine preferably includes a direct fuel injection system arranged to deliver fuel directly into the or each engine combustion chambers.
  • the fuel injection system is a spray guided fuel injection system.
  • the fuel injection system is a dual fluid or air-assisted fuel injection system.
  • the fuel injection system preferably is able to produce a fuel spray having droplets with a Sauter mean diameter of less than 20 microns.
  • the catalyst is preferably arranged as a close coupled catalyst in the exhaust system and is in close proximity to and downstream from the engine combustion chambers.
  • the close coupled catalyst is arranged within the exhaust system at a distance approximately 38 centimeters downstream of the engine combustion chambers.
  • the engine may also conveniently include an underbody catalyst arranged downstream from the close coupled catalyst.
  • the underbody catalyst may preferably be arranged within the exhaust system at a distance approximately 40 centimeters downstream from the close coupled catalyst.
  • the engine may preferably be a reciprocating piston-type four-stroke engine, though it is to be appreciated that the invention may have applicability to alternative engine arrangements including to engines operating according to the two-stroke cycle.
  • an electronic control unit for controlling the operation of an internal combustion engine, the engine including one or more combustion chambers and an exhaust system comprising at least an oxidation catalyst and being coupled to the engine for enabling the egress of exhaust combustion gases from the or each combustion chamber, wherein the ECU is adapted to control the engine such that the temperature of the exhaust combustion gases fed into the exhaust system exceed 400°C within approximately five seconds of starting said engine.
  • the ECU is adapted to operate said engine at near full load fuelling levels and with a spark timing after top dead center during at least a portion of the first twenty seconds of engine operation.
  • the spark timing is calibrated to be within the order of 20° to 30° after top dead center during this initial period of operation.
  • FIG. 1 is a schematic representation of a direct injection internal combustion engine having an exhaust after treatment system which includes a close coupled catalyst and an underbody catalyst;
  • FIG. 2 is a pictorial representation of the exhaust after treatment system of Figure 1;
  • FIG. 3 is a graph depicting the cumulative engine-out hydrocarbon emissions by mass obtained from the operation of the direct injected engine represented in Figure 1 ;
  • - Figure 4 is a graph depicting the exhaust feed gas temperatures obtained from the operation of the direct injected engine represented in Figure 1 ;
  • - Figure 5 is a graph depicting the rise in operating temperature of the close coupled catalyst of the direct injected engine represented in Figure 1 during initial operation thereof; and
  • - Figure 6 is graph depicting the post catalyst cumulative hydrocarbon emissions by mass obtained from the operation of the direct injected engine represented in Figure 1.
  • the internal combustion engine 120 is one form of a direct injection (Dl) engine in which fuel is injected directly into the one or more combustion chambers 126 of the engine 120 by way of a Dl fuel injection system.
  • the fuel injection system is arranged on a cylinder head 85 of the engine 120 with the cylinder head 85 also accommodating one or more spark plugs 90 which are operatively arranged with respect to the or each combustion chamber 126 of the engine 120.
  • the engine 120 is a four-cylinder engine with individual combustion chambers 126 communicating with the exhaust system 100 by way of an exhaust manifold 200 having respective individual exhaust runner pipes 201.
  • the main embodiment will be described with reference to a four cylinder engine, it is of course to be appreciated that the present invention is equally applicable to other multi-cylinder engine configurations (such as for example six and eight cylinder engines) and may also be adapted for use with single cylinder engines.
  • Typical Dl engines such as that depicted in Figures 1 and 2 have the capacity to operate with a stratified distribution of fuel and air in each combustion chamber 126 thereof over a significant portion of the operating load and speed range of the engine.
  • a stratified distribution within the or each combustion chamber 126 may consist of a first region having a stoichiometric or near stoichiometric air fuel ratio (AFR) and a second region which contains lower concentrations of fuel and has a very lean air fuel ratio.
  • AFR stoichiometric or near stoichiometric air fuel ratio
  • the air and fuel mixture in the combustion chamber 126 has an overall lean air fuel ratio. Accordingly, such direct injection engines are commonly referred to as lean burn' engines due to this capacity to operate with an overall lean air fuel ratio in the combustion chambers 126 thereof.
  • such engines are designed so that the stoichiometric or near stoichiometric mixture or charge is positioned within the combustion chamber 126 so that it may be readily ignited by a respective spark plug 90.
  • the ability to operate the engine 120 with a lean air fuel ratio means that the overall air / fuel charge in the combustion chambers 126 is oxygen rich compared with a stoichiometric air / fuel charge distributed homogenously throughout the combustion chambers 126.
  • manifold port injected engines typically operate predominantly as homogenous charge engines.
  • a stratified charge engine may be operated under certain part load conditions so that the quantity of fuel delivered to the engine is varied relatively independently of throttle position (ie. independently of the quantity of air induced into a combustion chamber for a combustion event).
  • An engine operated in this manner may be said to be operated in a "fuel led" mode.
  • Fuel led operation enables direct injection engines to achieve fuel economy benefits over traditional manifold injected engines and carburetor based engines whose fuelling levels are dependent on throttle position. By operating an engine independently of its throttle position, the pumping work of the engine can be reduced which can result in fuel economy advantages.
  • Direct injection engines may utilise different mechanisms to generate a stratified mixture of fuel and air in a combustion chamber, such as spray guided (or jet guided) mechanisms, wall guided mechanisms and air guided (or motion guided) mechanisms.
  • Spray guided mechanisms such as that depicted in Figures 1 and 2 typically comprise a fuel injector which is located in an axial or near axial position relative to the combustion chamber.
  • a spark plug is typically located downstream from a nozzle of the fuel injector so that spray issuing from the fuel injector passes over a spark gap of the spark plug. In this way,- the spark plug and fuel injector are arranged so that the fuel spray can be ignited as it issues from the fuel injector.
  • the fuel spray issuing from the injector can be ignited directly by the spark plug without first requiring deflection off any other surfaces in the combustion chamber.
  • ignition occurs after the fuel injector has ceased operation or immediately prior to the fuel injector ceasing operation.
  • An engine combustion system designed in this manner to directly ignite a fuel spray as it issues from an injector is commonly referred to as a 'spray guided' combustion system.
  • the Dl fuel system shown in Figures 1 and 2 comprises a plurality of individual direct fuel injectors 20 which are each operatively arranged to deliver fuel into a respective combustion chamber 126 of the engine 120.
  • the direct fuel injectors 20, together with their corresponding combustion chambers 126 and spark plugs 90, represent one form of spray guided combustion system.
  • each spark plug 90 is arranged within a corresponding combustion chamber 126 such that it is able to directly ignite the fuel spray which issues from the axially arranged fuel injector 20.
  • the fuel injector 20 may be of any suitable type (eg. a single fluid or dual fluid delivery device) which is able to achieve suitable atomization of the fuel when delivered to the combustion chamber 126 to enable the direct ignition thereof by the spark plug 90.
  • fuel injectors 20 form part of an air assist or dual fluid fuel injection system 10 wherein compressed air is used to entrain and deliver a metered quantity of fuel into each combustion chamber 126 of the engine 120.
  • fuel injector 20 is a dual fluid fuel injector which incorporates a holding chamber which is in constant communication with a source of compressed air thereby placing the chamber at an elevated pressure relative to atmosphere.
  • the fuel injector 20 is in communication with a compressor 11 by way of an air-fuel rail 12 and air delivery conduit 13. A predetermined quantity of fuel is metered into the holding chamber against the pressure of the compressed air from a fuel metering means 15.
  • the fuel metering means 15 receives fuel from a fuel tank 16 via a fuel delivery line 17 and the air-fuel rail 12. Typically this occurs when the holding chamber is shut off from the combustion chamber 126.
  • a suitably located air-fuel pressure regulator 18 ensures the fuel pressure is maintained at a predetermined level above the air pressure such that the fuel can be satisfactorily metered into the fuel/delivery injector 20.
  • the fuel injector 20 can be opened thus communicating the holding chamber with the combustion chamber 126, with the pressure differential between the holding chamber and the combustion chamber 126 causing the compressed air to be expelled from the injector 20 into the combustion chamber 126.
  • the compressed air that flows into the combustion chamber 126 also carries the fuel from the holding chamber into the combustion chamber 126 as the metered fuel is atomised and entrained with the compressed air as the compressed air is expelled into the combustion chamber 126.
  • Such dual fluid injection systems are often referred to as low pressure direct injection systems as the pressure of the compressed air is typically less than the pressure used in single fluid direct injection systems (ie. systems that simply inject gasoline directly into a combustion chamber using a pressure time metering principle).
  • Such dual fluid injection systems typically produce fuel spray plumes having droplets with a Sauter mean diameter of less than approximately 20 microns. Further detail on the configuration and operation of dual fluid direct injection fuel systems such as that discussed with reference to Figure 1 may be found in the Applicant's US Patent No. RE 36768 & Published PCT Patent Application No. WO99/28621 , the contents of which are included herein by way of reference.
  • the exhaust system 100 is designed to treat the by-products of combustion (ie. typically a mixture of hot gases) which result after the combustion of the fuel delivered by the fuel injector 20. That is, the exhaust system 100 is effectively an exhaust after treatment system which serves to process the exhaust emissions produced by the engine 120 prior to their delivery into the atmosphere via the exhaust tailpipe 101.
  • the after treatment system includes a close coupled catalyst 105 and an underbody catalyst 115, though it is to be appreciated that the present invention may equally apply to other catalyst combinations or configurations. For example, the present invention is equally applicable where no underbody catalyst is included in the exhaust system 100.
  • Each of the close coupled and underbody catalysts 105, 115 are housed in corresponding housings 106, 116 which are arranged at specific points along the exhaust system 100.
  • the close coupled catalyst 105 is located upstream of the underbody catalyst 115 so as to receive raw emissions from the engine 120.
  • the emissions which are output from the close coupled catalyst 105 may be referred to as 'intermediate emissions'.
  • the close coupled catalyst 105 is located in close proximity to the exhaust ports of the engine 120 and in certain applications may be a three way catalyst (TWC).
  • the underbody catalyst 115 is located downstream of the close coupled catalyst 105 and is typically selected to promote further treatment of the intermediate emissions. Gases treated by the underbody catalyst 115 are expelled to atmosphere as tail-pipe exhaust gases via the tailpipe 101.
  • the underbody catalyst 115 may be a lean NOx catalyst (LNC).
  • the exhaust after treatment system 100 communicates with exhaust ports (not shown) of the engine 120 by way of the exhaust manifold 200.
  • the exhaust manifold 200 is connected to an engine block (not shown) by way of an exhaust manifold inlet coupling 215 and at an opposite outlet end is connected to a manifold extension pipe 205 by way of a manifold outlet coupling 230.
  • the manifold extension pipe 205 feeds into a close coupled catalyst inlet pipe 240 which is connected to the housing 106 of the close coupled catalyst 105 by way of an inlet coupling 210. In this way, raw engine out emissions produced during engine operation are able to be fed to the close coupled catalyst 105.
  • the housing 106 Downstream of the close coupled catalyst 105, the housing 106 is coupled to an intermediate extension pipe 250 which is in turn coupled to the housing 116 of the underbody catalyst 105 such that any intermediate emissions can be passed to the underbody catalyst 115.
  • the inlet coupling 210 is arranged approximately 38 centimetres (15 inches) downstream from the exhaust manifold inlet coupling 215. That is, the distance from the engine exhaust ports to the front of the housing 106 for the close coupled catalyst 105 is effectively 38 centimetres (15 inches). Furthermore, the length of the intermediate extension pipe 250 is arranged to be approximately 40 centimetres (15.5 inches), this dimension being the effective distance from the rear of the housing 106 to the front of the housing 116 for the underbody catalyst 115.
  • the exhaust treatment system 100 includes front and a rear gas composition sensors 110 and 135 respectively.
  • These sensors 110, 135 may be provided as "oxygen" or "O 2 " sensors which are well known devices in the automotive industry and typically used to determine the composition of gases at a particular point of an exhaust system.
  • the front oxygen sensor 110 is located along the close coupled catalyst inlet pipe 240 at a location adjacent the inlet to the housing 106 of the close coupled catalyst 105.
  • the rear oxygen sensor 135 is located along the intermediate extension pipe 250 of the exhaust system 100 at a location adjacent an outlet of the housing 106 of the close coupled catalyst 105.
  • AFR closed loop air fuel ratio
  • Such closed loop AFR control involves monitoring of the output of the oxygen sensor 110 to ensure that the air fuel ratio input to the engine combustion chambers 126 is stoichiometric.
  • closed loop AFR control is used under high load homogenous operating conditions.
  • the rear oxygen sensor 135 may be used to indicate the amount of oxygen in the partially treated exhaust gases that are expelled from the close coupled catalyst 105 and thereby passed to the underbody catalyst 115.
  • the housing 116 of the underbody catalyst 115 may also be arranged to receive a first catalyst temperature sensor 185 that can permit the temperature of the catalyst 115 to be monitored.
  • An electronic control unit (ECU) 190 is operatively coupled with respect to the engine 120 so as to control the overall operation thereof.
  • the operation of each of the direct fuel injectors 20, fuel metering means 15 and spark plugs 90 are directly or indirectly controlled by the ECU in accordance with specific operating conditions and requirements.
  • each of the front and rear oxygen sensors 110, 135 respectively, first catalyst temperature sensor 185 and other electronically actuated components and sensors are monitored by and/or are under the control of the ECU 190 such that it may effect engine control in a desired manner.
  • the ECU 190 controls operation of the engine 120 by actuating components of the engine 120 such as the fuel injectors 20 and spark plugs 90 at appropriate points in time and in response to prevailing engine operating conditions.
  • Such engine control is typically effected by the implementation of various control strategies that are stored within a memory component of the ECU and accessed and run by a processing means within the ECU.
  • the ECU 190 is programmed, and functions, to control the operation of the engine 120 so as to minimise the level of harmful exhaust emissions which are emitted to the atmosphere whilst still facilitating acceptable or desired engine performance in respect of fuel consumption, overall power output and driveability.
  • the engine 120 and exhaust treatment system 100 are designed such that operation of the engine 120 according to certain predetermined engine control strategies will enable certain low exhaust emissions targets to be realised.
  • preferred embodiments include the ECU 190 controlling the engine 120 so as to reduce the time required for catalyst light-off to occur within the exhaust after treatment system 100.
  • the ECU 190 is programmed and functions to reduce the time required for the close coupled catalyst 105 to achieve the light-off condition. Reduced catalyst light-off time is understood to assist with achieving elements of the stringent ULEV II and SULEV emission requirements.
  • the FTP drive cycle also requires that the vehicle (and hence engine) commences operation from a cold start and must initially operate at idle for a certain period of time.
  • a "cold start” can essentially be defined by the temperature of the engine and vehicle having stabilized at between approximately 20°C and 25°C (ie. the engine is not "warm” from recent operation).
  • One typical way of achieving this condition is by allowing the vehicle (and hence engine) to soak at these or similar temperatures for 10 hours (or an effective equivalent of this duration).
  • the period of idle operation following engine starting runs for approximately 20 seconds (including cranking time).
  • the SULEV emissions standard effectively requires the amount of NMOG, NOx and CO expelled in the engine exhaust tail-pipe emissions to be below certain legislated limits over 120,000 miles (193,121 km) of vehicle/engine life. In regard to the legislated NMOG limit, this is set at 0.01 g/mile for the SULEV requirements. Hence, no more than 0.1106g of NMOG is permitted to be emitted in the engine exhaust tail-pipe emissions over the entire FTP drive cycle if the vehicle is to satisfy the SULEV NMOG emissions requirement.
  • the ULEV II emissions standard similarly effectively requires the amount of NMOG, NOx and CO expelled in the engine exhaust tail-pipe emissions to be below certain legislated limits, although it specifies two tiers of requirements based on 50,000 miles (80,467 km) and 120,000 miles of vehicle/engine life.
  • 50,000 miles the NMOG emissions limit is set at 0.04 g/mile, whilst for 120,000 miles, the NMOG emissions limit is slightly higher and set at 0.055 g/mile.
  • the ECU 190 implements control strategies such that exhaust feed gas produced by the engine 120 is provided to the exhaust system 100 at elevated temperatures compared at least with those typically occurring at start-up of the engine 120 if such control strategies were not implemented. That is, the combustion event in each engine cylinder or combustion chamber 126 is controlled such that the temperatures of the gases resulting from combustion which are delivered to the exhaust system 100 via the exhaust manifold 200 are increased. Such elevation of the temperature of the exhaust feed gas may be achieved through increasing the fuelling rate of the engine 120 to a level above that which would otherwise be expected under typical operating conditions whilst simultaneously retarding ignition to after top dead centre.
  • Retarding ignition to after top dead centre reduces the torque generated by a combustion event (thus counter-acting the typical increase in torque normally associated with an increase in fuelling rate) whilst increasing the temperature of the exhaust feed gas delivered into the exhaust system 100 and hence which enters the close coupled catalyst 105.
  • the exhaust feed gas serves to heat the close coupled catalyst 105 at an elevated rate compared to when the engine 120 is operated with typical fuelling levels and typical ignition timings.
  • the close coupled catalyst 105 is able to achieve its light-off condition much sooner than would otherwise occur.
  • the chemical conversion processes which occur at the close coupled catalyst 105 as the exhaust gases come into contact with the substrate thereof are able to take place a very short time following engine start-up and hence significantly reduce the occurrence of untreated exhaust gases from being emitted into the atmosphere.
  • Similar comments apply in respect of the underbody catalyst 115.
  • the ability to effect and control such rapid catalyst light-off is an important component of being able to achieve the legislated low emissions standards.
  • ignition timings in the order of 20° to 30° ATDC (after top dead centre), with direct injection timings optimised to promote a fuel rich mixture at the spark plug 90 during said ignition timings, are appropriate to achieve these objectives. It is however to be understood that these timings may vary depending on outlet valve timings and other engine properties.
  • the overall air/fuel ratio for the engine 120 is set to slightly lean of the stoichiometric ratio during implementation of the catalyst light-off strategy.
  • the rapid light-off strategy discussed hereinbefore has been found to perform particularly well with certain physical arrangements of the close coupled catalyst 105 within the exhaust after treatment system 100. Though not limited to any specific dimensions or locations, arrangements of the close coupled catalyst 105 within the exhaust system 100 at a distance of about 38 centimetres (15 inches) downstream from the engine exhaust ports have proved successful. Similarly, arrangements of the underbody catalyst 115 within the exhaust system 100 at a distance of about 40 centimetres (15.5 inches) downstream from the close coupled catalyst 105 have proved effective.
  • certain catalyst volumes when arranged within the exhaust system 100 have proved effective in facilitating achievement of the SULEV and ULEV II NMOG emissions requirements.
  • Preferred embodiments utilise a catalyst which has a volume of 40% to 85% of the engine swept volume (ie. a certain percentage of the engine displacement).
  • the close coupled catalyst 105 has a volume which is less than 85% of the engine swept volume and which is preferably in the range of 50% to 60% of the engine swept volume.
  • the cell density of a typical catalyst used in the exhaust system 100 is approximately 400 cells per inch (CPI).
  • the close coupled catalyst 105 may be a catalyst which is at least able to effect oxidation of the exhaust gases which are delivered thereto.
  • the close coupled catalyst 105 will be a three way catalyst (TWC), the likes of which are well known in the automotive industry.
  • the underbody catalyst 115 will be a Lean NOx Trap (LNT) or the like. Again, such catalyst technologies are well know in the automotive industry.
  • FIG. 3 there is shown a graph 300 of the accumulated engine out total hydrocarbons (THC) which were recorded from the testing of the Applicant's Dl engine.
  • the accumulated engine out hydrocarbons are measured by mass in grams for an engine of a preferred embodiment such as the engine 120 described with reference to Figures 1 and 2 over a window of approximately 20 seconds from starting.
  • the curve 305 depicts the cumulative engine out hydrocarbon emissions achieved by the engine 120.
  • a majority of HC tail-pipe emissions are likely to be produced before the one or more catalysts 105, 115 of the after treatment system 100 have reached their light-off temperature, it is important to reduce the engine out HC emissions during this period before the catalysts have attained the light-off state, particularly in regard to the close coupled catalyst 105.
  • a maximum of 50% of the total SULEV NMOG emission mass permitted over a single drive cycle (which equates to 0.09g with the FTP weighted factor) was used as a threshold target for the amount of total HC emissions generated by the engine 120 before light-off of the close coupled catalyst 105 was achieved.
  • the close coupled catalyst 105 was a TWC having a cell density of 400 CPI and having a light-off temperature of 300°C. Referring to Figure 5, it is evident that the light-off time for the close coupled catalyst 105 was approximately 9 seconds. Noting this light-off time of 9 seconds, a consideration of curve 305 of graph 300 shows that the engine out HC mass before the close coupled catalyst 105 had attained the light-off condition was 0.05g. This is well below the target of 0.09g which was set. Over the first twenty seconds of engine operation, the engine 120 produced approximately 0.10 grams of hydrocarbons.
  • FIG. 4 there is shown a graph 400 of the exhaust feed gas temperature measured from the testing of the Applicant's Dl engine over a twenty second operating window from engine starting.
  • the curve 405 depicts the exhaust feed gas temperature (measured in degrees Celsius (°C)) for an engine of a preferred embodiment such as the engine 120 discussed above where the exhaust temperature is measured at a point 34 centimetres (13.5 inches) downstream from the engine cylinder head 85 (ie. and hence at a point adjacent to and upstream of the front of the close coupled catalyst 105).
  • the measurement of exhaust feed gas for the engine 120 remained at ambient temperature for approximately the first 2 seconds of engine operation. After this, the measured temperature of the exhaust feed gas rose to a peak temperature of between 750°C and 800°C and of approximately 770°C within approximately 15 seconds of starting. The temperature of the exhaust feed gas produced by the engine 120 exceeded approximately 500°C within the first 5 seconds of engine operation and thereafter exceeded 700°C within 10 seconds of engine operation. Within 20 seconds of starting and after the peak temperature had been reached, the exhaust feed gas temperature dropped below 700°C.
  • FIG. 5 there is shown a graph 500 which depicts catalyst temperature resulting from the testing of the Applicant's Dl engine over a twenty second operating window from engine starting.
  • the curve 505 depicts the rate of rise in the operating temperature (measured in degrees Celsius (°C)) for the close coupled catalyst 105 of an engine of a preferred embodiment such as the engine 120 discussed above.
  • the close coupled catalyst 105 tested was a TWC having a cell density of 400 CPI and was located in the exhaust system 100 a distance of approximately 38 centimetres (15 inches) downstream of the engine exhaust ports.
  • the measured operating temperature of the close coupled catalyst 105 initially remained at ambient temperature for approximately the first two seconds of engine operation. Thereafter, the operating temperature of the catalyst rose steadily to a temperature of between 550°C and 600°C and of approximately 580°C after 20 seconds of engine operation. After 5 seconds the catalyst temperature was approximately 150°C, after 10 seconds the temperature was approximately 350°C and after 15 seconds the temperature was approximately 490°C.
  • the operating temperature of the close coupled catalyst 105 has a more linear profile than the profile of the exhaust feed gas temperature due to the effects of thermal inertia of the catalyst 105 and exhaust system 100. Nonetheless, it is evident that the light-off time (ie. the time taken for the operating temperature to reach 300°C) for the close coupled catalyst 105 was only 9 seconds. Hence, under the control of the ECU 190, operation of the engine 120 within the first few seconds following start-up resulted in significantly high exhaust feed gas temperatures being produced such that effective operation of the close coupled catalyst 105 was able to be achieved in a short time. This of course minimises the amount of untreated exhaust emissions passing through the exhaust system 100 and entering the atmosphere.
  • FIG. 6 there is shown a graph 600 which depicts the cumulative post catalyst hydrocarbon emissions resulting from the testing of the Applicant's Dl engine.
  • the post catalyst accumulated engine out hydrocarbons as depicted by curve 605 are measured by mass in grams for an engine of a preferred embodiment such as the engine 120 described above over a window of approximately 20 seconds from starting.
  • the post catalyst accumulated hydrocarbons were measured within the exhaust system 100 at a point downstream of the close coupled catalyst 105 and upstream of the underbody catalyst 115.
  • the cumulative emissions downstream of the close coupled catalyst 105 were approximately 0.028g.
  • the cumulative emissions were approximately 0.052g and after 15 seconds they were approximately 0.063g.
  • the post catalyst cumulative emissions curve 605 flattens out considerably after approximately 10 seconds as approximately 75% of the total HC emissions were produced within the first 10 seconds of starting.
  • the Dl engine requires to be designed and controlled such that, as well as being able to facilitate rapid light-off of the close coupled catalyst 105 in the exhaust system 100, the level of HC emissions produced by the engine 120 during the initial period following engine start-up and prior to catalyst light-off can be minimised. In this way, it can be ensured that overall engine operation does not result in the production of engine exhaust tail-pipe emissions being delivered to the atmosphere which would exceed the legislated requirements.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

Cette invention se rapporte à un moteur à combustion interne (120) comprenant une ou plusieurs chambres de combustion (126) et un système d'échappement (100) contenant au moins un catalyseur d'oxydation (105). Le système d'échappement (100) est couplé au moteur (120) pour permettre l'émission des gaz d'échappement provenant de la combustion dans la chambre de combustion ou dans chacune des chambres de combustion (126) du moteur (120). Le moteur (120) comprend également une unité de commande électronique ou ECU (190) servant à commander le fonctionnement du moteur (120), cette unité ECU (190) étant destinée à commander le moteur (120) pour que la température des gaz d'échappement provenant de la combustion et introduits dans le système d'échappement (100) dépassent 400 °C pendant environ cinq secondes après le démarrage du moteur (120). La température de fonctionnement du catalyseur (105) est de préférence apte à dépasser environ 300°C pendant environ dix secondes de fonctionnement du moteur.
PCT/AU2003/001035 2002-08-15 2003-08-15 Reduction des emissions pour moteur a combustion interne WO2004016917A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003249788A AU2003249788A1 (en) 2002-08-15 2003-08-15 Emissions control for an internal combustion engine

Applications Claiming Priority (2)

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AU2002950810A AU2002950810A0 (en) 2002-08-15 2002-08-15 Emissions control for an internal combustion engine
AU2002950810 2002-08-15

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111502803A (zh) * 2019-01-31 2020-08-07 现代自动车株式会社 用于稀燃发动机的后处理系统和后处理方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5577383A (en) * 1991-09-20 1996-11-26 Hitachi, Ltd. Apparatus for controlling internal combustion engine
US5655365A (en) * 1993-01-25 1997-08-12 Orbital Engine Company (Australia) Pty. Limited Method of operating an internal combustion engine
WO2001018374A1 (fr) * 1999-09-08 2001-03-15 Orbital Engine Company (Australia) Pty Limited Traitement de gaz d'echappement et dispositif
WO2001029406A1 (fr) * 1999-10-18 2001-04-26 Orbital Engine Company (Australia) Pty Limited Injection directe de carburants dans des moteurs a combustion interne
EP0719937B1 (fr) * 1994-12-28 2002-04-10 Mazda Motor Corporation Méthode et système pour purifier les gaz d'échappement pour véhicules automobiles

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5577383A (en) * 1991-09-20 1996-11-26 Hitachi, Ltd. Apparatus for controlling internal combustion engine
US5655365A (en) * 1993-01-25 1997-08-12 Orbital Engine Company (Australia) Pty. Limited Method of operating an internal combustion engine
EP0719937B1 (fr) * 1994-12-28 2002-04-10 Mazda Motor Corporation Méthode et système pour purifier les gaz d'échappement pour véhicules automobiles
WO2001018374A1 (fr) * 1999-09-08 2001-03-15 Orbital Engine Company (Australia) Pty Limited Traitement de gaz d'echappement et dispositif
WO2001029406A1 (fr) * 1999-10-18 2001-04-26 Orbital Engine Company (Australia) Pty Limited Injection directe de carburants dans des moteurs a combustion interne

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111502803A (zh) * 2019-01-31 2020-08-07 现代自动车株式会社 用于稀燃发动机的后处理系统和后处理方法

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