WO2008047017A1 - System for treating the exhaust gases of a turbocharged diesel engine - Google Patents

System for treating the exhaust gases of a turbocharged diesel engine Download PDF

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Publication number
WO2008047017A1
WO2008047017A1 PCT/FR2007/051987 FR2007051987W WO2008047017A1 WO 2008047017 A1 WO2008047017 A1 WO 2008047017A1 FR 2007051987 W FR2007051987 W FR 2007051987W WO 2008047017 A1 WO2008047017 A1 WO 2008047017A1
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WIPO (PCT)
Prior art keywords
turbine
engine
catalytic oxidation
catalytic
treatment
Prior art date
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PCT/FR2007/051987
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French (fr)
Inventor
Christophe Met
Isabelle Louis-Rose
Najat Moral-Mouaddib
Original Assignee
Renault S.A.S
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Publication of WO2008047017A1 publication Critical patent/WO2008047017A1/en

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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
    • F01N3/02—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
    • F01N3/023—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 using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—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 using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—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 using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • 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
    • F01N3/02—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
    • F01N3/022—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • 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
    • F01N3/023—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 using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/0231—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 using means for regenerating the filters, e.g. by burning trapped particles using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
    • 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
    • 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
    • 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
    • F01N3/103—Oxidation catalysts for HC and CO only
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/108—Auxiliary reduction catalysts
    • 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
    • F01N3/2033—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using a fuel burner or introducing fuel into exhaust duct
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/02—Combinations of different methods of purification filtering and catalytic conversion
    • 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
    • F01N2340/00—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses
    • F01N2340/06—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses characterised by the arrangement of the exhaust apparatus relative to the turbine of a turbocharger
    • 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
    • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
    • 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
    • F01N2610/04—Adding substances to exhaust gases the substance being hydrogen
    • 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

  • the invention relates to a system for treating the exhaust gases of a turbocharged diesel engine.
  • the toughening of automobile pollution control standards requires the incorporation of specialized aftertreatment devices into the exhaust system of motor vehicles in order to meet the objectives of low emissions of exhaust pollutants.
  • oxidation catalysts to reduce hydrocarbon (HC) and carbon oxides (CO x ) emissions
  • SCRs selective reduction catalysts
  • NO x nitrogen
  • particle filtration systems for the removal of soot produced during combustion.
  • the NO x traps are regenerated by denitration and / or desulfation under reducing conditions (HC, CO, H2, ...) at temperatures higher than those encountered in the exhaust, in particular for the desulfation (0 up to 700 VS).
  • Particulate filters are regenerated by increasing the temperature to about 600 0 C to allow the removal of soot stored by oxygen.
  • a fuel injector at the level of the exhaust line should make it possible to reduce the engine stresses, for example by avoiding the complicated single or multiple fuel injection strategies in the combustion chamber of the engine, which positively influences the durability of the engine, in particular by a low dilution of the fuel in the oil.
  • Other methods include varying the fuel injection into the engine combustion chamber using delayed injection strategies or post fuel injections to obtain the exotherm required for fuel injection by the engine. 'injector placed in the exhaust line, downstream of the oxidation catalyst and upstream of the after-treatment systems. These methods make it possible to reach a sufficient temperature in the exhaust line, but at the expense of the consumption and durability of the engine.
  • the object of the invention relates to a system for treating the exhaust gases of a turbocharged diesel engine provided with a turbine and a compressor, said system comprising a fuel injector and one or more aftertreatment devices of the combustion gases placed on the exhaust line of the engine, characterized in that it comprises a catalytic oxidation device disposed upstream of the turbine of the turbocharger, and in that the fuel injector is disposed upstream of said catalytic oxidation device, the one or more post-treatment devices being located downstream of said turbine.
  • Such positioning according to the invention of the fuel injector at the exhaust, downstream of the exhaust manifold of the engine and upstream of the turbine, makes it possible to take maximum advantage of the engine heat, which makes possible an injection of fuel at any time during the engine cycle, without modifying the operating mode of the engine.
  • the additional catalytic oxidation device placed between the fuel injector and the turbine, makes it possible for it to generate the exotherm required for the after-treatment device (s) located downstream of the turbine.
  • this catalytic oxidation device has a sufficiently small volume not to oxidize all the hydrocarbons injected by the fuel injector.
  • the hydrocarbons that have not been completely oxidized can be used by the post-treatment device (s) located downstream of the turbine.
  • the catalytic oxidation device has a monolithic substrate with ultrafine walls (thickness less than 3 millinches).
  • a low pressure drop is obtained, which is important for the correct operation of the turbo and driving pleasure, and on the other hand a low thermal mass, which allows a better rise in temperature, and better cold efficiency;
  • the catalytic oxidation device comprises a catalytic formulation adapted to the oxidation of hydrocarbons
  • the catalytic formulation of the catalytic oxidation device can also be adapted to promote the production of reducing agents, in particular hydrogen,
  • the after-treatment device or devices situated downstream of the turbine are chosen from: a catalytic oxidation device, a catalytic reduction device, a nitrogen oxide trap, a particulate filter, these devices being able to be used; in any combination.
  • FIG. 1 is a diagrammatic representation of a system according to the invention
  • FIG. 2 is a graphical graph showing the HC emissions, downstream of a catalytic oxidation device comprising a Pt / Pd catalytic formulation, as a function of the volume of said device
  • FIG. 3 is a graphical curve representing HC emissions, downstream of a catalytic oxidation device comprising a catalytic formulation with base of Pt / Pd to reach a total exotherm of 650 0 C for different modes of engine operation.
  • FIG. 1 schematically represents a diesel engine 1 with a turbocharger 2, the latter comprising a compressor 3 and a turbine 4.
  • the turbine 4 is mounted on the exhaust line 5 of the engine, downstream of the exhaust manifold 6 of the latter.
  • FIG. 1 also represents a treatment system according to the invention of the exhaust gases of the diesel engine 1.
  • This system comprising a fuel injector 7 and an aftertreatment device 8 for the combustion gases placed on the exhaust line 5 of the engine.
  • the post-treatment device 8 may be dedicated to the oxidation or reduction treatment of HC, CO, NO x , particulate filtration, or may consist of any of the combinations of known treatment devices.
  • the fuel injector 7 is disposed upstream of an additional catalytic oxidation device 9 disposed upstream of the turbine 4 of the turbocharger, the post-treatment device 8 being located downstream of said turbine.
  • the fuel injector 7 at the exhaust is further connected to a control device 10 of the vehicle.
  • the catalytic oxidation device 9 has a sufficiently small volume not to oxidize all the hydrocarbons injected by the fuel injector.
  • a device 9 of small volume makes it possible to treat a part of the hydrocarbons injected by the fuel injector 7, and to further increase the thermal, the remaining hydrocarbons being used, if necessary, by the device of post treatment 8 located downstream of the turbine.
  • the volume of the catalytic oxidation device 9 is conditioned by the desired hydrocarbon treatment efficiency. It will also be partly conditioned by the available space upstream of the turbine.
  • the volume of the catalytic oxidation device (DOC) 9 is conditioned by the desired hydrocarbon treatment efficiency.
  • Lab tests with 9000 ppm oil injections and upstream temperature injector 7 of 350 0 C on Pt-based catalysts made it possible to demonstrate the interest of a small volume of treatment at the level of the catalytic oxidation device 9.
  • FIG. 2 represents the hydrocarbon emissions downstream of the catalytic oxidation device 9 as a function of the volume of the latter for different operating points of the engine, under the conditions set out above.
  • the curves 1, 2, 3 correspond to exhaust gas flow rates of 30, 65 and 100 kg / h respectively.
  • a catalytic oxidation device of small volume in particular between 0.05 and 0.3 L, makes it possible to retain a significant share of hydrocarbons, available for post-treatment devices disposed downstream of the turbine in the range. operating a motor.
  • a catalytic oxidation device 9 having a monolithic substrate with ultrafine walls and containing a catalytic formulation suitable for the oxidation of hydrocarbons (for example Pt / Pd-based, of transition metals, of oxides, of alumina) will be used. , rare earth etc.).
  • the ultrafine-walled monolithic substrate means that the thickness of the substrate is less than 3 milli inches (or 76 ⁇ m).
  • This type of wall makes it possible to limit the pressure drop, thus limiting the backpressure to the exhaust, as well as rapid heating up of the substrate.
  • the catalyst is almost "transparent" on the exhaust line because it generates less back pressure to the exhaust.
  • the rapid rise in temperature then makes it possible to vaporize the fuel injected at the right temperature.
  • One of the major interests of this invention is to reach sufficient temperatures at any time during the operation of the vehicle, without having recourse to specific operating strategies of the engine, so that the stresses exerted on the engine are lower, thus increasing its lifetime.
  • Such a catalytic device allows a very rapid rise in temperature and hydrocarbon treatment at startup with a limited impact on the operation of the turbocharger. From the small volume of the catalytic device, hydrocarbons partially or non-oxidized can be used by the post-treatment device (s) located downstream of the turbine.
  • Curve a represents the variation of the exhaust gas flow corresponding to different operating points of the engine.
  • Curve b represents the quantity (in ppm) of HC hydrocarbons emitted at the DOC outlet for the different points of operation of the engine.
  • the curve c represents the exhaust gas temperature at the input of the same DOC for the various points of operation of the engine.
  • the curve d represents the exhaust gas temperature at the DOC outlet for the various operating points of the engine.

Abstract

The invention relates to a system for treating the exhaust gases of a diesel engine (1) fitted with a turbocharger (2) equipped with a turbine (4) and with a compressor (3), said system comprising a fuel injector (7) and one or more devices (8) for the post-treatment of the combustion gases, this device or these devices being positioned in the exhaust line (5) of the engine, characterized in that it comprises an oxidation catalytic converter device (9) positioned upstream of the turbine (4) of the turbocharger and in that the fuel injector (7) is positioned upstream of said oxidation catalytic converter device (9), the post-treatment device or devices (8) being situated downstream of said turbine.

Description

SYSTEME DE TRAITEMENT DES GAZ D'ECHAPPEMENT D UN MOTEUR DIESEL A TURBOCOMPRESSEUR EXHAUST GAS TREATMENT SYSTEM OF A TURBOCHARGER DIESEL ENGINE
L'invention concerne un système de traitement des gaz d'échappement d'un moteur diesel à turbocompresseur.The invention relates to a system for treating the exhaust gases of a turbocharged diesel engine.
Le durcissement des normes en matière de dépollution automobile impose l'incorporation de dispositifs de post- traitement spécialisés dans la ligne d'échappement des véhicules automobiles afin de respecter les objectifs de faibles émissions de polluants à l'échappement.The toughening of automobile pollution control standards requires the incorporation of specialized aftertreatment devices into the exhaust system of motor vehicles in order to meet the objectives of low emissions of exhaust pollutants.
Les dispositifs de post- traitement couramment utilisés sont : des catalyseurs d'oxydation pour réduire les émissions d'hydrocarbures (HC) et d'oxydes de carbone (COx), des catalyseurs à réduction sélective (SCR) ou des pièges à oxydes d'azote (NOx) pour traiter les émissions de NOx, et des systèmes de filtration de particules pour l'élimination des suies produites lors de la combustion.The following commonly used aftertreatment devices are: oxidation catalysts to reduce hydrocarbon (HC) and carbon oxides (CO x ) emissions, selective reduction catalysts (SCRs) or oxidation oxide traps. nitrogen (NO x ) to treat NO x emissions, and particle filtration systems for the removal of soot produced during combustion.
Dans le cas des véhicules diesel, l'élimination des polluants réglementés nécessite l'utilisation de plusieurs dispositifs de posttraitement, comprenant en général un catalyseur d'oxydation en amont d'un piège à NOx et d'un filtre à particules. Ces dispositifs sont placés en aval de la turbine du turbocompresseur du moteur (FR 2 879 237, WO 2006/008599).In the case of diesel vehicles, the removal of regulated pollutants requires the use of several aftertreatment devices, usually including an oxidation catalyst upstream of an NO x trap and a particulate filter. These devices are placed downstream of the turbine of the engine turbocharger (FR 2 879 237, WO 2006/008599).
Cependant afin de maintenir les performances de ces dispositifs à leur niveau optimal, il est nécessaire de les régénérer régulièrement.However, in order to maintain the performance of these devices at their optimum level, it is necessary to regenerate them regularly.
Les pièges à NOx sont régénérés par dénitration et/ou désulfatation en milieu réducteur (HC, CO, H2, ...) à des températures supérieures à celles rencontrées dans l'échappement, en particulier pour la désulfatation (jusqu'à 7000C).The NO x traps are regenerated by denitration and / or desulfation under reducing conditions (HC, CO, H2, ...) at temperatures higher than those encountered in the exhaust, in particular for the desulfation (0 up to 700 VS).
Les filtres à particules sont régénérés par accroissement de la température jusqu'à environ 6000C afin de permettre l'élimination des suies stockées par l'oxygène.Particulate filters are regenerated by increasing the temperature to about 600 0 C to allow the removal of soot stored by oxygen.
Ces différentes phases de régénération requièrent une composition gazeuse particulière obtenue via un mode de fonctionnement particulier du moteur et/ ou l'injection de carburant au niveau de la ligne d'échappement, au moyen d'un injecteur situé en amont du dispositif de post- traitement. L'accroissement de température est obtenu grâce à l'oxydation exothermique des HC et CO lors de leur passage dans le catalyseur d'oxydation.These different regeneration phases require a particular gaseous composition obtained via a particular mode of operation of the engine and / or the injection of fuel at the level of the exhaust line, by means of an injector located upstream of the post-injection device. treatment. The temperature increase is obtained by the exothermic oxidation of HC and CO during their passage in the oxidation catalyst.
Ces différentes stratégies d'aide à la régénération peuvent toutefois s'avérer insuffisantes en conditions de roulages critiques, par exemple en ville ou dans des embouteillages, pour élever suffisamment la température des gaz. Il en résulte des régénérations longues, voire incomplètes, qui impactent fortement les autres prestations moteurs, telle que la consommation et la durabilité.However, these different strategies for regeneration assistance may be insufficient in critical driving conditions, for example in cities or in traffic jams, to raise the temperature of the gases sufficiently. This results in long or incomplete regenerations, which have a strong impact on other motor services, such as consumption and durability.
L'utilisation d'un injecteur de carburant au niveau de la ligne d'échappement devrait permettre de diminuer les contraintes moteurs, en s 'affranchissant par exemple des stratégies compliquées de post injection de carburant simples ou multiples dans la chambre de combustion du moteur, ce qui influe positivement sur la durabilité du moteur, notamment par une faible dilution du carburant dans l'huile.The use of a fuel injector at the level of the exhaust line should make it possible to reduce the engine stresses, for example by avoiding the complicated single or multiple fuel injection strategies in the combustion chamber of the engine, which positively influences the durability of the engine, in particular by a low dilution of the fuel in the oil.
Toutefois, l'utilisation de ce type d 'injecteur pose un certain nombre de problèmes. Ainsi, la vaporisation du carburant dans la ligne d'échappement est particulièrement délicate en raison des faibles températures atteintes dans l'échappement, notamment dans les conditions de roulage critiques, ce qui favorise la formation de dépôts carbonés indésirables dans les systèmes de post-traitement en aval. Il est également difficile d'obtenir un mélange homogène avec les gaz d'échappement, ce qui est nécessaire pour maximiser l'efficacité de conversion des hydrocarbures injectés dans le catalyseur d'oxydation, et donc l'exotherme généré.However, the use of this type of injector poses a number of problems. Thus, the vaporization of the fuel in the exhaust line is particularly difficult because of the low temperatures reached in the exhaust, especially in critical driving conditions, which promotes the formation of undesirable carbonaceous deposits in the post-treatment systems. downstream. It is also difficult to obtain a homogeneous mixture with the exhaust gases, which is necessary to maximize the conversion efficiency of the hydrocarbons injected into the oxidation catalyst, and therefore the generated exotherm.
Une solution pour résoudre ces difficultés consiste à n'injecter du carburant dans la ligne d'échappement que lorsque la température est supérieure à 3000C, ce qui correspond à des conditions de roulage favorables.One solution for solving these difficulties is to inject fuel into the exhaust line only when the temperature is above 300 ° C., which corresponds to favorable driving conditions.
Les méthodes existantes pour élargir la gamme d'utilisation de ce type d'injecteur consistent principalement à mettre en place un système de pilotage approprié n'autorisant la réalisation des opérations de régénération que dans des conditions particulières de fonctionnement moteur.The existing methods to widen the range of use of this type of injector mainly consist in setting up an appropriate control system authorizing the carrying out of the regeneration operations only in particular conditions of engine operation.
D'autres méthodes consistent à faire varier l'injection de carburant dans la chambre de combustion du moteur en utilisant des stratégies d'injections retardées ou de post injections du carburant afin d'obtenir l'exotherme nécessaire à l'injection de carburant par l'injecteur placé dans la ligne d'échappement, en aval du catalyseur d'oxydation et en amont des systèmes de post-traitement. Ces méthodes permettent d'atteindre une température suffisante dans la ligne d'échappement, mais au détriment de la consommation et de la durabilité du moteur.Other methods include varying the fuel injection into the engine combustion chamber using delayed injection strategies or post fuel injections to obtain the exotherm required for fuel injection by the engine. 'injector placed in the exhaust line, downstream of the oxidation catalyst and upstream of the after-treatment systems. These methods make it possible to reach a sufficient temperature in the exhaust line, but at the expense of the consumption and durability of the engine.
Ces solutions ne permettent pas d'exploiter de manière optimale le potentiel de l'injecteur de carburant à l'échappement puisque sa mise en service dépend de stratégies de contrôle moteur afin d'atteindre une valeur de température minimale dans la ligne d'échappement avant toute injection de carburant. Par ailleurs, ces méthodes alourdissent la charge de calcul du dispositif de gestion du fonctionnement du moteur et tendent à dégrader les performances du moteur en terme de consommation et durabilité du moteur lors de régénérations en conditions de roulage critiques.These solutions do not make optimal use of the potential of the fuel injector at the exhaust since its commissioning depends on engine control strategies to achieve a minimum temperature value in the front exhaust line. any fuel injection. Furthermore, these methods increase the computational load of the engine operation management device and tend to degrade the engine performance in terms of engine consumption and durability during regenerations in critical driving conditions.
Il s'avère donc nécessaire de trouver des stratégies d'élévation des niveaux thermiques des gaz d'échappement lors des roulages critiques permettant une injection de carburant au niveau de l'échappement à n'importe quel moment du cycle moteur, sans contrôle spécifique afin d'apporter la souplesse nécessaire au fonctionnement de systèmes de post- traitement de plus en plus complexes.It is therefore necessary to find strategies for raising the thermal levels of the exhaust gases during critical runs that allow fuel to be injected at the level of the exhaust at any moment of the engine cycle, without any specific control. to provide the necessary flexibility for the operation of increasingly complex post-processing systems.
A cet effet, l'objet de l'invention concerne un système de traitement des gaz d'échappement d'un moteur diesel à turbocompresseur pourvu d'une turbine et d'un compresseur, ledit système comprenant un injecteur de carburant et un ou plusieurs dispositifs de post-traitement des gaz de combustion placés sur la ligne d'échappement du moteur, caractérisé en ce qu'il comporte un dispositif catalytique d'oxydation disposé en amont de la turbine du turbocompresseur, et en ce que l'injecteur de carburant est disposé en amont dudit dispositif catalytique d'oxydation, le ou les dispositifs de post traitement étant situés en aval de ladite turbine.For this purpose, the object of the invention relates to a system for treating the exhaust gases of a turbocharged diesel engine provided with a turbine and a compressor, said system comprising a fuel injector and one or more aftertreatment devices of the combustion gases placed on the exhaust line of the engine, characterized in that it comprises a catalytic oxidation device disposed upstream of the turbine of the turbocharger, and in that the fuel injector is disposed upstream of said catalytic oxidation device, the one or more post-treatment devices being located downstream of said turbine.
Un tel positionnement selon l'invention de l'injecteur de carburant à l'échappement, en aval du collecteur d'échappement du moteur et en amont de la turbine, permet de profiter au maximum des thermiques moteurs, ce qui rend possible une injection de carburant à n'importe quel moment du cycle moteur, sans modification du mode de fonctionnement du moteur.Such positioning according to the invention of the fuel injector at the exhaust, downstream of the exhaust manifold of the engine and upstream of the turbine, makes it possible to take maximum advantage of the engine heat, which makes possible an injection of fuel at any time during the engine cycle, without modifying the operating mode of the engine.
Le dispositif catalytique d'oxydation supplémentaire, placé entre l'injecteur de carburant et la turbine, permet quant à lui de générer l'exotherme nécessaire au(x) dispositifs) de post-traitement situés en aval de la turbine.The additional catalytic oxidation device, placed between the fuel injector and the turbine, makes it possible for it to generate the exotherm required for the after-treatment device (s) located downstream of the turbine.
Avantageusement, ce dispositif catalytique d'oxydation présente un volume suffisamment faible pour ne pas oxyder la totalité des hydrocarbures injectés par l'injecteur de carburant.Advantageously, this catalytic oxidation device has a sufficiently small volume not to oxidize all the hydrocarbons injected by the fuel injector.
Ainsi, les hydrocarbures qui n'ont pas été complètement oxydés peuvent être utilisés par le(s) dispositifs) de post-traitement situés en aval de la turbine.Thus, the hydrocarbons that have not been completely oxidized can be used by the post-treatment device (s) located downstream of the turbine.
Le système de traitement selon l'invention présente une ou plusieurs des caractéristiques suivantes :The treatment system according to the invention has one or more of the following characteristics:
- le dispositif catalytique d'oxydation présente un substrat monolithique à parois ultrafines (épaisseur inférieure à 3 milli inch). On obtient ainsi d'une part une faible perte de charge, ce qui est important pour le bon fonctionnement du turbo et l'agrément de conduite, et d'autre part une faible masse thermique, ce qui permet une meilleure montée en température, et une meilleure efficacité à froid ;the catalytic oxidation device has a monolithic substrate with ultrafine walls (thickness less than 3 millinches). Thus, on the one hand, a low pressure drop is obtained, which is important for the correct operation of the turbo and driving pleasure, and on the other hand a low thermal mass, which allows a better rise in temperature, and better cold efficiency;
- le dispositif catalytique d'oxydation comprend une formulation catalytique adaptée à l'oxydation des hydrocarbures,the catalytic oxidation device comprises a catalytic formulation adapted to the oxidation of hydrocarbons,
- la formulation catalytique du dispositif catalytique d'oxydation peut également être adaptée afin de favoriser la production de réducteurs, notamment l'hydrogène,the catalytic formulation of the catalytic oxidation device can also be adapted to promote the production of reducing agents, in particular hydrogen,
- le ou les dispositifs de post-traitement situés en aval de la turbine sont choisis parmi : un dispositif catalytique d'oxydation, un dispositif catalytique de réduction, un piège à oxydes d'azote, un filtre à particules, ces dispositifs pouvant être utilisés dans n'importe quelle combinaison.the after-treatment device or devices situated downstream of the turbine are chosen from: a catalytic oxidation device, a catalytic reduction device, a nitrogen oxide trap, a particulate filter, these devices being able to be used; in any combination.
L'invention est maintenant décrite en référence aux dessins annexés, non limitatifs, dans lesquels : la figure 1 est une représentation schématique d'un système selon l'invention ; la figure 2 est une courbe graphique représentant les émissions de HC, en aval d'un dispositif catalytique d'oxydation comprenant une formulation catalytique à base de Pt/Pd, en fonction du volume dudit dispositif ; la figure 3 est une courbe graphique représentant les émissions de HC, en aval d'un dispositif catalytique d'oxydation comprenant une formulation catalytique à base de Pt/Pd pour atteindre un exotherme total de 6500C pour différents modes de fonctionnement moteur.The invention is now described with reference to the accompanying non-limiting drawings, in which: FIG. 1 is a diagrammatic representation of a system according to the invention; FIG. 2 is a graphical graph showing the HC emissions, downstream of a catalytic oxidation device comprising a Pt / Pd catalytic formulation, as a function of the volume of said device; FIG. 3 is a graphical curve representing HC emissions, downstream of a catalytic oxidation device comprising a catalytic formulation with base of Pt / Pd to reach a total exotherm of 650 0 C for different modes of engine operation.
La figure 1 représente schématiquement un moteur diesel 1 à turbocompresseur 2, ce dernier comprenant un compresseur 3 et une turbine 4. De manière classique, la turbine 4 est montée sur la ligne d'échappement 5 du moteur, en aval du collecteur d'échappement 6 de ce dernier.FIG. 1 schematically represents a diesel engine 1 with a turbocharger 2, the latter comprising a compressor 3 and a turbine 4. In a conventional manner, the turbine 4 is mounted on the exhaust line 5 of the engine, downstream of the exhaust manifold 6 of the latter.
La figure 1 représente également un système de traitement selon l'invention des gaz d'échappement du moteur diesel 1. Ce système comprenant un injecteur de carburant 7 et un dispositif de posttraitement 8 des gaz de combustion placés sur la ligne d'échappement 5 du moteur. Le dispositif de post- traitement 8 peut être dédié au traitement par oxydation ou réduction des HC, CO, NOx, à la filtration des particules, ou peut consister en n'importe laquelle des combinaisons des dispositifs de traitement connus.FIG. 1 also represents a treatment system according to the invention of the exhaust gases of the diesel engine 1. This system comprising a fuel injector 7 and an aftertreatment device 8 for the combustion gases placed on the exhaust line 5 of the engine. The post-treatment device 8 may be dedicated to the oxidation or reduction treatment of HC, CO, NO x , particulate filtration, or may consist of any of the combinations of known treatment devices.
Selon l'invention, l'injecteur de carburant 7 est disposé en amont d'un dispositif catalytique d'oxydation supplémentaire 9 disposé en amont de la turbine 4 du turbocompresseur, le dispositif de post traitement 8 étant situé en aval de ladite turbine.According to the invention, the fuel injector 7 is disposed upstream of an additional catalytic oxidation device 9 disposed upstream of the turbine 4 of the turbocharger, the post-treatment device 8 being located downstream of said turbine.
L'injecteur de carburant 7 à l'échappement est en outre relié à un dispositif de contrôle 10 du véhicule.The fuel injector 7 at the exhaust is further connected to a control device 10 of the vehicle.
Le dispositif catalytique d'oxydation 9 présente un volume suffisamment faible pour ne pas oxyder la totalité des hydrocarbures injectés par l'injecteur de carburant.The catalytic oxidation device 9 has a sufficiently small volume not to oxidize all the hydrocarbons injected by the fuel injector.
L'utilisation d'un dispositif 9 de faible volume permet de traiter une partie des hydrocarbures injectés par l'injecteur de carburant 7, et d'accroître davantage la thermique, les hydrocarbures restant étant utilisés, le cas échéant, par le dispositif de post- traitement 8 situé en aval de la turbine.The use of a device 9 of small volume makes it possible to treat a part of the hydrocarbons injected by the fuel injector 7, and to further increase the thermal, the remaining hydrocarbons being used, if necessary, by the device of post treatment 8 located downstream of the turbine.
Notamment, le volume du dispositif catalytique d'oxydation 9 est conditionné par l'efficacité de traitement des hydrocarbures souhaité. Il sera également en partie conditionné par la place disponible en amont de la turbine.In particular, the volume of the catalytic oxidation device 9 is conditioned by the desired hydrocarbon treatment efficiency. It will also be partly conditioned by the available space upstream of the turbine.
Comme indiqué plus haut, le volume du dispositif catalytique d'oxydation (DOC) 9 est conditionné par l'efficacité de traitement souhaitée des hydrocarbures. Des tests en laboratoire avec des injections d'hydrocarbures de 9000 ppm et une température en amont de l'injecteur 7 de 3500C sur des catalyseurs à base de Pt ont permis de mettre en évidence l'intérêt d'un faible volume de traitement au niveau du dispositif catalytique d'oxydation 9.As indicated above, the volume of the catalytic oxidation device (DOC) 9 is conditioned by the desired hydrocarbon treatment efficiency. Lab tests with 9000 ppm oil injections and upstream temperature injector 7 of 350 0 C on Pt-based catalysts made it possible to demonstrate the interest of a small volume of treatment at the level of the catalytic oxidation device 9.
Les résultats de ces tests sont représentés sur la figure 2, qui représente les émissions d'hydrocarbures en aval du dispositif catalytique d'oxydation 9 en fonction du volume de ce dernier pour différents points de fonctionnement du moteur, dans les conditions énoncées précédemment.The results of these tests are shown in FIG. 2, which represents the hydrocarbon emissions downstream of the catalytic oxidation device 9 as a function of the volume of the latter for different operating points of the engine, under the conditions set out above.
Les courbes 1, 2, 3 correspondent à des débits de gaz d'échappement de 30, 65 et 100 kg/h respectivement.The curves 1, 2, 3 correspond to exhaust gas flow rates of 30, 65 and 100 kg / h respectively.
Ainsi, un dispositif d'oxydation catalytique de faible volume, notamment compris entre 0,05 et 0,3 L, permet de conserver une part d'hydrocarbures significative, disponible pour les dispositifs de post traitement disposés en aval de la turbine dans la gamme de fonctionnement d'un moteur.Thus, a catalytic oxidation device of small volume, in particular between 0.05 and 0.3 L, makes it possible to retain a significant share of hydrocarbons, available for post-treatment devices disposed downstream of the turbine in the range. operating a motor.
On utilisera un dispositif catalytique d'oxydation 9 présentant un substrat monolithique à parois ultrafines et contenant une formulation catalytique adaptée à l'oxydation des hydrocarbures (par exemple à base de Pt/ Pd, de métaux de transition, d'oxydes, d'alumine, de terres rares etc.). Le substrat monolithique à parois ultrafines signifie que l'épaisseur du substrat est inférieure à 3 milli inch (ou 76μm). Ce type de parois permet de limiter la perte de charge, limitant ainsi la contre- pression à l'échappement, ainsi qu'une mise en température rapide du substrat. Ainsi le catalyseur est quasiment « transparent » sur la ligne d'échappement car il génère moins de contre-pression à l'échappement. La montée rapide en température permet alors de vaporiser le carburant injecté à la bonne température. Un des intérêts majeurs de cette invention est d'atteindre des températures suffisantes à tout moment du fonctionnement du véhicule, sans avoir recours à des stratégies spécifiques de fonctionnement du moteur, de sorte que les contraintes exercées sur le moteur sont plus faibles, augmentant ainsi sa durée de vie.A catalytic oxidation device 9 having a monolithic substrate with ultrafine walls and containing a catalytic formulation suitable for the oxidation of hydrocarbons (for example Pt / Pd-based, of transition metals, of oxides, of alumina) will be used. , rare earth etc.). The ultrafine-walled monolithic substrate means that the thickness of the substrate is less than 3 milli inches (or 76μm). This type of wall makes it possible to limit the pressure drop, thus limiting the backpressure to the exhaust, as well as rapid heating up of the substrate. Thus the catalyst is almost "transparent" on the exhaust line because it generates less back pressure to the exhaust. The rapid rise in temperature then makes it possible to vaporize the fuel injected at the right temperature. One of the major interests of this invention is to reach sufficient temperatures at any time during the operation of the vehicle, without having recourse to specific operating strategies of the engine, so that the stresses exerted on the engine are lower, thus increasing its lifetime.
Un tel dispositif catalytique permet une montée très rapide en température et un traitement des hydrocarbures au démarrage avec un impact limité sur le fonctionnement du turbocompresseur. Du £εtit du faible volume du dispositif catalytique, les hydrocarbures partiellement ou non oxydés peuvent être utilisés par le(s) dispositifs) de posttraitement situé(s) en aval de la turbine.Such a catalytic device allows a very rapid rise in temperature and hydrocarbon treatment at startup with a limited impact on the operation of the turbocharger. From the small volume of the catalytic device, hydrocarbons partially or non-oxidized can be used by the post-treatment device (s) located downstream of the turbine.
La capacité d'un catalyseur à base de Pt/Pd pour générer un exotherme suffisant au fonctionnement de dispositifs post traitement en aval a été étudiée sur banc moteur.The ability of a Pt / Pd catalyst to generate a sufficient exotherm for the operation of downstream post-treatment devices has been studied on the engine test bench.
Cette étude a été réalisée pour un DOC d'un volume de 0,8 litre avec des températures variables en amont du DOC. Dans ce cas précis, l'injection d'hydrocarbures est ajustée pour atteindre 650°c en aval du DOC.This study was carried out for a DOC of a volume of 0.8 liter with variable temperatures upstream of DOC. In this case, the hydrocarbon injection is adjusted to 650 ° C downstream of the DOC.
Les résultats sont représentés sur la figure 3.The results are shown in Figure 3.
La courbe a représente la variation du débit de gaz d'échappement correspondant à différents points de fonctionnement du moteur.Curve a represents the variation of the exhaust gas flow corresponding to different operating points of the engine.
La courbe b représente la quantité (en ppm) d'hydrocarbures HC émis en sortie du DOC pour les différents points de fonctionnement du moteur.Curve b represents the quantity (in ppm) of HC hydrocarbons emitted at the DOC outlet for the different points of operation of the engine.
La courbe c représente la température des gaz d'échappement en entrée du même DOC pour les différents points de fonctionnement du moteur.The curve c represents the exhaust gas temperature at the input of the same DOC for the various points of operation of the engine.
La courbe d représente la température des gaz d'échappement en sortie du DOC pour les différents points de fonctionnement du moteur.The curve d represents the exhaust gas temperature at the DOC outlet for the various operating points of the engine.
On constatera que, pour tous les points de fonctionnement du moteur, y compris ceux pour lesquels la température en entrée du DOC est faible, il est possible d'obtenir avec une injection d'hydrocarbures adaptée : une température en sortie de l'ordre de 6500C, suffisante pour assurer le fonctionnement des dispositifs de post traitement situés en aval de la turbine, et des émissions d'hydrocarbures en aval du dispositif catalytique d'oxydation limitées (inférieures à 2500 ppm) mais suffisamment importantes pour permettre le cas échéant, le fonctionnement des dispositifs de post traitement situés en aval de la turbine.It will be noted that for all operating points of the engine, including those for which the DOC inlet temperature is low, it is possible to obtain with a suitable hydrocarbon injection: a temperature at the output of the order of 650 0 C, sufficient to ensure the operation of post-treatment devices located downstream of the turbine, and hydrocarbon emissions downstream of the catalytic oxidation device limited (less than 2500 ppm) but large enough to allow if necessary , the operation of post-treatment devices located downstream of the turbine.
On pourra par ailleurs adapter la formulation du catalyseur d'oxydation utilisé afin de favoriser également la production de It will also be possible to adapt the formulation of the oxidation catalyst used in order to also favor the production of

Claims

réducteurs très réactifs, tels que l'hydrogène, dont l'impact positif est connu sur les dispositifs de purifications des oxydes d'azote. REVENDICATIONS highly reactive reducing agents, such as hydrogen, whose positive impact is known on nitrogen oxide purification devices. CLAIMS
1. Système de traitement des gaz d'échappement d'un moteur diesel (1) à turbocompresseur (2) pourvu d'une turbine (4) et d'un compresseur (3), ledit système comprenant un injecteur de carburant (7) et un ou plusieurs dispositifs de post- traitement (8) des gaz de combustion placés sur la ligne d'échappement (5) du moteur, caractérisé en ce qu'il comporte un dispositif catalytique d'oxydation (9) disposé en amont de la turbine (4) du turbocompresseur, en ce que l'injecteur de carburant (7) est disposé en amont dudit dispositif catalytique d'oxydation (9), le ou les dispositifs de post traitement (8) étant situés en aval de ladite turbine, et en ce que le dispositif catalytique d'oxydation (9) présente un substrat monolithique à parois ultrafines.An exhaust gas treatment system of a turbocharged diesel engine (1) having a turbine (4) and a compressor (3), said system comprising a fuel injector (7) and one or more after-treatment devices (8) for the combustion gases placed on the exhaust line (5) of the engine, characterized in that it comprises a catalytic oxidation device (9) arranged upstream of the engine, turbine (4) of the turbocharger, in that the fuel injector (7) is arranged upstream of said catalytic oxidation device (9), the post-treatment device (s) (8) being located downstream of said turbine, and in that the catalytic oxidation device (9) has a monolithic substrate with ultrafine walls.
2. Système de traitement selon la revendication 1, caractérisé en ce que le dispositif catalytique d'oxydation (9) présente un volume suffisamment faible pour ne pas oxyder la totalité des hydrocarbures injectés par l'injecteur de carburant (7).2. Treatment system according to claim 1, characterized in that the catalytic oxidation device (9) has a sufficiently small volume not to oxidize all hydrocarbons injected by the fuel injector (7).
3. Système de traitement selon l'une des revendications 1 ou 2, caractérisé en ce que dispositif catalytique d'oxydation (9) comprend une formulation catalytique adaptée à l'oxydation des hydrocarbures.3. Treatment system according to one of claims 1 or 2, characterized in that catalytic oxidation device (9) comprises a catalytic formulation suitable for the oxidation of hydrocarbons.
4. Système de traitement selon la revendication 3, caractérisé en ce que la formulation catalytique du dispositif catalytique d'oxydation est également adaptée afin de favoriser la production de réducteurs.4. Treatment system according to claim 3, characterized in that the catalytic formulation of the catalytic oxidation device is also adapted to promote the production of reducing agents.
5. Système de traitement selon la revendication 4, caractérisé en ce que la formulation catalytique du dispositif catalytique d'oxydation est également adaptée afin de favoriser la production d'hydrogène.5. Treatment system according to claim 4, characterized in that the catalytic formulation of the catalytic oxidation device is also adapted to promote the production of hydrogen.
6. Système de traitement selon l'une des revendications 1 à 5, caractérisé en ce que le ou les dispositifs de post- traitement (8) situés en aval de la turbine sont choisis parmi : un dispositif catalytique d'oxydation, un dispositif catalytique de réduction, un piège à oxydes d'azote, un filtre à particules. 6. Treatment system according to one of claims 1 to 5, characterized in that the after-treatment device (s) (8) located downstream of the turbine are selected from: a catalytic oxidation device, a catalytic device reduction, a nitrogen oxide trap, a particulate filter.
PCT/FR2007/051987 2006-10-17 2007-09-21 System for treating the exhaust gases of a turbocharged diesel engine WO2008047017A1 (en)

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