WO2000077354A1 - Systeme d'evacuation des gaz d'echappement pour moteur a combustion interne de vehicule automobile - Google Patents

Systeme d'evacuation des gaz d'echappement pour moteur a combustion interne de vehicule automobile Download PDF

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Publication number
WO2000077354A1
WO2000077354A1 PCT/EP2000/005120 EP0005120W WO0077354A1 WO 2000077354 A1 WO2000077354 A1 WO 2000077354A1 EP 0005120 W EP0005120 W EP 0005120W WO 0077354 A1 WO0077354 A1 WO 0077354A1
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WO
WIPO (PCT)
Prior art keywords
heat exchanger
flow
exhaust
cross
exhaust system
Prior art date
Application number
PCT/EP2000/005120
Other languages
German (de)
English (en)
Inventor
Katrin Schaper
Original Assignee
Emitec Gesellschaft Für Emissionstechnologie Mbh
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Filing date
Publication date
Application filed by Emitec Gesellschaft Für Emissionstechnologie Mbh filed Critical Emitec Gesellschaft Für Emissionstechnologie Mbh
Publication of WO2000077354A1 publication Critical patent/WO2000077354A1/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
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F01N3/2046—Periodically cooling catalytic reactors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9481—Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0093—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are of the same type
    • 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
    • F01N3/0205—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust using heat exchangers
    • 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
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • 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
    • F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
    • 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
    • F01N3/101—Three-way 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
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/02—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a heat exchanger
    • 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
    • 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
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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 present invention relates to an exhaust system for an internal combustion engine of a motor vehicle, in particular for diesel or lean-burn engines, with at least one first catalytic converter and ⁇ Ox storage arranged in an exhaust line, which is also referred to as ⁇ Ox adsorber, at least in front of the ⁇ Ox storage a heat exchanger is arranged in the exhaust line.
  • a three-way catalytic converter is usually used in current motor vehicles, by means of which carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides ( ⁇ Ox) are converted into harmless components.
  • EP 0 298 240 B1 describes that, in the known exhaust gas catalytic converter systems, the determination of the residual oxygen content in the exhaust gas by means of an oxygen probe, the determination of the temperature profile on the catalyst and the determination of the amount of heat released in the catalytic reaction to the exhaust gas behavior of the Internal combustion engine can be closed.
  • EP 0 628 134 B1 discloses adsorbers for storing those that occur during the cold start phase to use unburned hydrocarbons which are released again when the downstream catalytic converter is ready for operation.
  • TA-Luft applies to stationary internal combustion engines in Germany.
  • the reduction of nitrogen oxide emissions from the exhaust gas of internal combustion engines is often achieved with urea in stationary systems.
  • the normal operating temperature range within which such NOx stores operate reliably is currently around 150 ° C to 550 ° C, with an increase in the upper temperature to e.g. 700 ° C through new coatings. Above a maximum temperature, currently around 800 ° C, NOx stores are damaged, so that such temperatures are to be avoided in any case.
  • Such NOx stores are usually arranged behind a first catalytic converter in the exhaust system of a motor vehicle.
  • the reaction taking place in the first catalyst, in particular the hydrocarbons with oxygen, is exothermic, so that a heat flow is supplied to the exhaust gas when the exhaust gas is cleaned in the catalyst. Since the NOx accumulator only reaches its minimum operating temperature at a temperature of approx. 150 ° C, it is desirable, above all In view of the cold start behavior of such an exhaust gas purification system, things should be arranged as closely as possible behind the first catalytic converter.
  • the heat exchanger is preferably designed as a countercurrent heat exchanger, in particular as a double-walled tube, through which exhaust gas flows in its interior and a cooling fluid flows through it in the shell formed by the double wall (so-called tube bundle heat exchanger).
  • the heat exchanger is a piece of the exhaust line which is designed as a finned tube and around which a cooling fluid flows (so-called finned heat exchanger).
  • the object of the present invention to provide an exhaust gas system with an improved, in particular higher and more cost-effective, cooling capacity Specify in order to avoid thermal damage to a NOx accumulator arranged in the exhaust system, in particular premature aging of the coating.
  • the temperature field of the NOx store should be able to be maintained from approximately 150 ° C. to approximately 550 ° C.
  • existing substances such as unburned hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gas of diesel and lean-burn engines should be removed as far as possible during all load conditions of the internal combustion engine, and rapid operational readiness after the cold start should be ensured.
  • Damage to the NOx accumulator arranged in the exhaust system in the present case has cross-flow heat exchangers used according to the invention for two fluids exchanging in cross-flow with layers of structured, in particular corrugated, sheets which are layered in a crosswise manner and which form a multiplicity of flowable channels and between which are arranged in smooth sheets at least the following advantages of a high / ⁇ T, a small mass, a small ⁇ , a small space requirement and a small heat sink.
  • the NOx store is preferably arranged between the first catalyst and a second catalyst and the cross-flow heat exchanger upstream of the first catalyst or between the first catalyst and the NOx store.
  • the proportion of energy that is dissipated as heat flow in front of the NOx storage device is based on the temperature limits of approx. 150 ° C to 550 ° C of the normal function or the maximum temperature of 800 ° C of the NOx storage device.
  • the cross-flow heat exchanger arranged between the first catalyst and the NOx store, it can be avoided that the NOx store experiences a thermal load that goes beyond the limit temperature of approximately 800 ° C.
  • the exhaust gas flow is discharged in two stages.
  • the two-stage removal of the heat flow can take place by two cross-flow heat exchangers arranged directly one behind the other in front of the NOx store, or by one cross-flow heat exchanger in front of the first catalytic converter and between the first catalytic converter and the NOx store.
  • the outlet temperature of the exhaust gas can also be lowered in a targeted manner behind the first catalytic converter, which is arranged upstream of the NOx accumulator, for example when the internal combustion engine is under high load.
  • the removal of a heat flow from the exhaust gas upstream of the NOx accumulator can advantageously be carried out more flexibly by the two-stage process.
  • the flexibility is somewhat less if only a cross-flow heat exchanger is arranged in front of the NOx store between the internal combustion engine and the first catalytic converter.
  • the temperature of the first catalytic converter can be reduced in such a way that the NOx store is not thermally overloaded, ie its temperature is kept below 800 ° C.
  • both the first catalyst and the second catalyst can each be designed as three-way catalysts.
  • the NOx trap and the second catalytic converter can be integrated in one unit. This can be achieved, for example, in that the NOx storage has a three-way coating.
  • the NOx accumulator on the one hand adsorbs NOx and on the other hand acts as an oxidation catalyst, with adsorbed NOx being directly reacted with hydrocarbons.
  • the heat flow to be dissipated by the cross-flow heat exchanger is preferably in the range from approximately 5 kW to approximately 50 kW.
  • the channels of the cross-flow heat exchanger which are provided for the exhaust gas fluid to flow through are arranged essentially in the flow direction of the exhaust gas in the exhaust line.
  • a sloping flow of the exhaust gas on the exhaust gas inlet side of the cross-flow heat exchanger is proposed, i.e. the channels of the cross-flow heat exchanger intended for the throughflow of the exhaust gas fluid are preferably arranged in the exhaust line at an angle to the flow direction of the exhaust gas, preferably at an angle of 45 °.
  • the cooling fluid is preferably air which, under normal conditions of the internal combustion engine, passes through the channels provided for this purpose
  • Cross-flow heat exchanger flows essentially without constraint.
  • Air as a cooling fluid has, for example, in particular the advantage over water that any leaks in the cross-flow heat exchanger which are caused by production and / or which have been caused by the operating time are generally not critical.
  • a sufficient heat dissipation for normal conditions can be achieved if the channels of the cross-flow heat exchanger provided for a flow of air essentially in the direction of travel of the
  • Motor vehicle are arranged in the exhaust system.
  • the channels of the cross-flow heat exchanger intended for air to flow through the exhaust gas line at an angle to the direction of travel of the motor vehicle, preferably at an angle of 45 ° are arranged.
  • a fan can be provided, for example, which preferably starts up in a load-dependent manner similar to a cooling system for internal combustion engines.
  • the cross-flow heat exchanger have a cell density of at least 50 to 200 cells per square inch.
  • Fig.l a first embodiment of an exhaust system according to the invention.
  • FIG. 2 shows a second exemplary embodiment of an exhaust system according to the invention.
  • the exhaust gas passes from the crimping engine 1 into a
  • Exhaust line 5 in which a first catalytic converter 2 and a second catalytic converter 6 are arranged.
  • a NOx accumulator 4 is arranged between the two catalysts 2, 6.
  • a cross-flow heat exchanger 3 is arranged in the exhaust line 5 between the first catalytic converter 2 and the NOx store 4.
  • the exothermic reaction taking place in the first catalytic converter 2 is supplied with energy in the exhaust gas stream, so that its temperature rises.
  • two operating temperatures of approximately 1,000 ° C. or more occur at the downstream outlet of the first catalytic converter. Since the maximum temperature of the exhaust gas fluid after the first catalytic converter 2 is approximately 800 ° C., a NOx accumulator 4 arranged downstream in the exhaust gas line 5 with an operating temperature range of approximately 150 ° C. to approximately 550 ° C. would become prematurely due to such a high temperature destroyed or malfunctioning with the result that the exhaust gas flow could not be freed from the environmentally harmful NOx.
  • the cross-flow heat exchanger 3 is provided between the first catalytic converter 2 and the NOx store 4, by means of which a load-dependent removal of the heat flow W symbolically represented by an arrow can be implemented, in particular when the internal combustion engine 1 is under high load.
  • a heat exchanger can also be located before the first catalytic converter 2, provided that this does not have any disadvantages for the cold start behavior.
  • a controlled removal of the heat stream W is preferably carried out, so that it is ensured that the temperature of the NOx store is in the desired range Area remains. Since, at correspondingly high operating temperatures, the first catalyst 2 already oxidizes the unburned hydrocarbons contained in the exhaust gas stream and the carbon monoxide contained therein with a relatively high percentage, there are generally no longer sufficient quantities of unburned hydrocarbons for reaction with the one in the NOx store 4 stored NOx.
  • a second catalytic converter 6 is also provided downstream of the NOx accumulator 4, which also introduces the additional catalytic converters unburned hydrocarbons oxidized and thus provides an essentially cleaned exhaust gas.
  • FIG. 2 shows a further exemplary embodiment of an exhaust gas catalytic converter system according to the invention.
  • the exhaust gas stream is conducted from the internal combustion engine 1 into the exhaust pipe 5, in which two cross-flow heat exchangers 3, 8, a first catalytic converter 2 and a NOx accumulator 7 provided with a three-way catalytic converter coating are arranged.
  • a first cross-flow heat exchanger 3 is again arranged between the catalytic converter 2 and the NOx store 7. With this cross-flow heat exchanger 3 it is possible to remove a defined heat flow W2 from the exhaust gas flow in accordance with the respective operating load or the respective operating state of the internal combustion engine 1.
  • a further cross-flow heat exchanger 8 is provided between the internal combustion engine 1 and the catalytic converter 2, by means of which an additional heat flow W1 can be removed from the exhaust gas flow.
  • this leads to a decrease in the inlet temperature of the catalyst 2, which possibly also slows down the exothermic reaction taking place there.
  • its temperature at the outlet from the catalytic converter 2 is lower than in the case of the exemplary embodiment according to FIG. 1.
  • the heat flow W2 to be dissipated in the cross-flow heat exchanger 3 is therefore lower than in the exemplary embodiment according to FIG Figure 1.
  • the heat exchangers 3, 8 serve to reduce the maximum temperature of the exhaust gas flow when entering the NOx store 7, in order to ensure that its predeterminable temperature range is maintained.
  • a combined use of a cross-flow heat exchanger and a tube bundle and / or finned heat exchanger in the exhaust line 5 is also conceivable, especially if you want to use the thermal energy taken from the exhaust gas stream in the vehicle for heating purposes or the like.
  • the NOx store 7 is an integral unit with a three-way catalyst coating Mistake. This three-way catalytic converter coating acts like a main catalytic converter 6 according to FIG. 1, but with the advantage that fewer separate parts of the exhaust gas cleaning system are required.
  • the exhaust line 5 can also contain an exhaust gas turbocharger 9 behind the internal combustion engine 1.
  • the exhaust gas drives this turbocharger 9 so that ambient air is compressed there and is guided to the internal combustion engine 1 by an arrow. Excess air is usually blown off, so that it can advantageously be used according to the invention, also indicated by an arrow, for forced cooling of the exhaust gas in the exhaust line 5, for example in cross-flow in the additional cross-flow heat exchanger 8.
  • a blower 10 can also be provided to generate a forced flow.
  • Both of the exemplary embodiments described above are used to clean an exhaust gas stream of an internal combustion engine 1.
  • a heat flow is removed from the exhaust gas stream in front of a NOx accumulator 4, 7 by means of at least one cross-flow heat exchanger 3, 8.
  • the at least one cross-flow heat exchanger 3, 8 is not in operation, especially during the cold start phase, so that the operating temperature of the NOx accumulator 4, 7 is reached quickly support in the amount of at least approx. 150 ° C.
  • the use of at least one cross-flow heat exchanger 3, 8 in the exhaust system of an internal combustion engine 1 thus serves for operational safety or also to increase the service life of the NOx accumulator 4, 7. Reliable cleaning of the exhaust gas stream is thus achieved over the entire load range of the internal combustion engine 1.
  • the cross-flow heat exchanger 3, 8 can be designed so that it dissipates little heat due to its design alone at low temperatures and a lot of heat at high temperatures.
  • funnel-shaped, possibly variable, guide plates can be provided on the inlet side for the cooling fluid of the cross-flow heat exchanger 3, 8.
  • the temperature range of the NOx store 4, 7 serves as the control variable, in which it not only reliably adsorbs NOx but also works without damage, ie it is not thermally overloaded.
  • the regulation of the amount of heat to be dissipated in the operating temperature range of the NOx accumulator 4, 7 from approx. 150 ° C. to approx. 550 ° C. can be regulated in a manner known per se by determining the respective operating temperature by means of corresponding thermocouples, not shown, on whose For example, the amount of cooling fluid by means of which the heat flow is removed is regulated. In any case, the Avoid exceeding the maximum temperature of 800 ° C by increasing the heat dissipation.
  • the internal combustion engine 1 is preferably operated at an air / fuel ratio of lambda ⁇ 1 during the cold start until the NOx store 4, 7 has reached its minimum operating temperature of approx. 150 ° C.
  • the internal combustion engine 1 By operating the internal combustion engine 1 in the rich, or at least in the stoichiometric operating range, there will be sufficient unburned hydrocarbons in the exhaust gas which serve to rapidly increase the operating temperature of the first catalytic converter 2 connected upstream of the NOx accumulator. Due to the rapid increase in the operating temperature of the first catalytic converter 2, the operating temperature of the NOx store 4, 7 of at least approximately 150 ° C. is reached relatively quickly.
  • the NOx store 4, 7 preferably stores NOx and oxidizes unburned hydrocarbons.
  • the NOx store 4, 7 can be regenerated by briefly adding hydrocarbons to the exhaust gas. This means that the stored NOx serves as a source of oxygen due to the oxidation of unburned hydrocarbons taking place in the NOx store and thus nitrogen, water and CO 2 escape from the NOx store 4, 7. After the NOx has been “expelled” from the NOx store 4, 7 in this way, the NOx store 4, 7 again has its original adsorption capacity for NOx supplied by the internal combustion engine 1 in the exhaust gas. This indicates an amount intended for regeneration When hydrocarbons also reach the NOx store 4, 7, it is expedient if the first catalytic converter 2 has only a low storage capacity for oxygen, so that the hydrocarbons are not already oxidized there and are therefore virtually wasted. Overall, the present invention permits simple and effective compliance with a predetermined temperature range of temperature-sensitive components in an exhaust gas system, such as that of a NOx accumulator 4, 7, while at the same time ensuring the quality of the exhaust gas cleaning under different operating conditions.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

L'invention concerne un système d'évacuation des gaz d'échappement d'un moteur à combustion interne (1) d'un véhicule automobile, qui peut être utilisé en particulier pour des moteurs diesel ou à mélange pauvre. Ce système d'évacuation des gaz d'échappement comprend au moins un premier catalyseur (2) et un premier accumulateur de NOx (7) placés chaque fois dans une branche d'évacuation des gaz d'échappement (5). Dans la branche d'évacuation de gaz d'échappement (5), avant l'accumulateur de NOx (7), est disposé au moins un échangeur de chaleur (3; 8) qui, selon l'invention, se présente sous la forme d'un échangeur de chaleur à courants inversés (3; 8) destiné à un écoulement des gaz d'échappement se faisant en sens inverse par rapport à un fluide de refroidissement, avec échange de chaleur, de telle sorte que le courant de chaleur (W1, W2) évacué est tel qu'une température maximale de l'accumulateur de NOx (7) n'est pas dépassée. La présente invention permet globalement un respect simple et efficace d'une plage de température prédéterminée pour des composants sensibles à la température dans un système d'évacuation des gaz d'échappement tel que le ou les accumulateurs de NOx (7) et assure simultanément la qualité de la purification des gaz d'échappement dans diverses conditions de fonctionnement.
PCT/EP2000/005120 1999-06-15 2000-06-05 Systeme d'evacuation des gaz d'echappement pour moteur a combustion interne de vehicule automobile WO2000077354A1 (fr)

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DE19927246.8 1999-06-15
DE19927246A DE19927246A1 (de) 1999-06-15 1999-06-15 Abgassystem für eine Verbrennungskraftmaschine eines Kraftfahrzeuges

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DE102006057662A1 (de) * 2006-12-07 2008-06-12 Bayerische Motoren Werke Ag Fahrzeug mit einem thermoelektrischen Generator
US9091193B2 (en) 2013-12-13 2015-07-28 Cnh Industrial America Llc Systems and methods for cooling a diesel exhaust fluid dosing module of an agricultural vehicle

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DE10145916B4 (de) * 2001-09-18 2014-01-02 Volkswagen Ag Verfahren und Vorrichtung zum Abkühlen einer Katalysatoreinrichtung
DE10161398A1 (de) * 2001-12-13 2003-06-18 Volkswagen Ag Verfahren und Vorrichtung zum Kühlen einer Katalysatoreinrichtung
FR2884555A1 (fr) * 2005-04-13 2006-10-20 Peugeot Citroen Automobiles Sa Dispositif de recuperation d'energie d'un moteur a combustion interne
JP4281789B2 (ja) 2006-12-06 2009-06-17 トヨタ自動車株式会社 排気熱回収装置
DE102016215290B4 (de) 2016-08-16 2018-10-04 Continental Automotive Gmbh Komponente eines Abgassystems und Verfahren zur Abgasnachbehandlung
DE102017123916B4 (de) 2017-10-13 2019-07-25 Dr. Ing. H.C. F. Porsche Aktiengesellschaft Abgasanlage einer Brennkraftmaschine mit Katalysator

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DE102006057662A1 (de) * 2006-12-07 2008-06-12 Bayerische Motoren Werke Ag Fahrzeug mit einem thermoelektrischen Generator
US9091193B2 (en) 2013-12-13 2015-07-28 Cnh Industrial America Llc Systems and methods for cooling a diesel exhaust fluid dosing module of an agricultural vehicle

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