EP2098697B1 - Exhaust system of an internal combustion engine - Google Patents
Exhaust system of an internal combustion engine Download PDFInfo
- Publication number
- EP2098697B1 EP2098697B1 EP08425083A EP08425083A EP2098697B1 EP 2098697 B1 EP2098697 B1 EP 2098697B1 EP 08425083 A EP08425083 A EP 08425083A EP 08425083 A EP08425083 A EP 08425083A EP 2098697 B1 EP2098697 B1 EP 2098697B1
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- EP
- European Patent Office
- Prior art keywords
- tabs
- exhaust system
- exhaust
- tubular body
- exhaust duct
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
- 238000002485 combustion reaction Methods 0.000 title claims description 11
- 230000003068 static effect Effects 0.000 claims description 20
- 239000003054 catalyst Substances 0.000 claims description 17
- 230000003197 catalytic effect Effects 0.000 claims description 11
- 230000003647 oxidation Effects 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 238000011144 upstream manufacturing Methods 0.000 claims description 8
- 241000826860 Trapezium Species 0.000 claims description 2
- 239000000654 additive Substances 0.000 claims 1
- 230000000996 additive effect Effects 0.000 claims 1
- 239000007789 gas Substances 0.000 description 22
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 18
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 10
- 239000004202 carbamide Substances 0.000 description 10
- 229910021529 ammonia Inorganic materials 0.000 description 8
- 239000003638 chemical reducing agent Substances 0.000 description 7
- 239000000243 solution Substances 0.000 description 6
- OWIKHYCFFJSOEH-UHFFFAOYSA-N Isocyanic acid Chemical compound N=C=O OWIKHYCFFJSOEH-UHFFFAOYSA-N 0.000 description 5
- XLJMAIOERFSOGZ-UHFFFAOYSA-N anhydrous cyanic acid Natural products OC#N XLJMAIOERFSOGZ-UHFFFAOYSA-N 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 238000006116 polymerization reaction Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- VPKDCDLSJZCGKE-UHFFFAOYSA-N methanediimine Chemical compound N=C=N VPKDCDLSJZCGKE-UHFFFAOYSA-N 0.000 description 2
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 2
- 230000008719 thickening Effects 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/431—Straight mixing tubes with baffles or obstructions that do not cause substantial pressure drop; Baffles therefor
- B01F25/4315—Straight mixing tubes with baffles or obstructions that do not cause substantial pressure drop; Baffles therefor the baffles being deformed flat pieces of material
-
- 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
- F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/21—Mixing gases with liquids by introducing liquids into gaseous media
- B01F23/213—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids
- B01F23/2132—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids using nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/314—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit
- B01F25/3141—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit with additional mixing means other than injector mixers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/431—Straight mixing tubes with baffles or obstructions that do not cause substantial pressure drop; Baffles therefor
- B01F25/43197—Straight mixing tubes with baffles or obstructions that do not cause substantial pressure drop; Baffles therefor characterised by the mounting of the baffles or obstructions
- B01F25/431974—Support members, e.g. tubular collars, with projecting baffles fitted inside the mixing tube or adjacent to the inner wall
-
- 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
- F01N3/24—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 constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2892—Exhaust flow directors or the like, e.g. upstream of catalytic device
-
- 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
- F01N2240/20—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 flow director or deflector
-
- 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
- F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
- F01N2570/14—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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
Definitions
- the present invention relates to an exhaust system of an internal combustion engine provided with an exhaust gas after-treatment arrangement.
- the present invention is advantageously intended for use in an exhaust system of an internal combustion engine provided with an exhaust gas after-treatment arrangement to which the following description specifically refers but without loss of generality.
- a problem associated with introducing an aqueous urea solution into the exhaust system is that the decomposition of the urea also results in the formation of isocyanic acid (HNCO), which tends to thicken and polymerize, building up on the inside walls of the exhaust system and resulting in the formation of solid deposits that are difficult to remove.
- HNCO isocyanic acid
- Patent application EP1514591A1 describes a mixer, which is arranged in an exhaust system of an internal combustion engine immediately upstream of an SCR catalyst into which the hot exhaust gas mixed with reducing agents is fed.
- patent applications EP1022048A1 , DE10060808A1 , WO0107763A1 , WO9913972A1 , WO9905402A1 , WO9905401A1 , EP1748162A1 , DE10248294A1 , WO0009869A1 , WO2005073524A1 , WO0112301A1 , EP0526392A1 , EP0894523A1 describe exhaust systems provided with mixers arranged close to reducing agent feeder devices.
- known mixers of the type described above have the drawback of not achieving an ideal balance between the opposing needs for effectiveness (i.e. to guarantee adequate mixing of the exhaust gas) and efficiency (i.e. to limit loss of pressure in the exhaust gas).
- known mixers of the type described above are either low in effectiveness (i.e. they do not guarantee adequate mixing of the exhaust gas) or low in efficiency (i.e. they cause high losses of pressure in the exhaust gas).
- WO2007127529A2 discloses an exhaust aftertreatment system including injection of chemical species; the system has a mixer provided by a stamped muffler flange and arranged in the exhaust pipe between the injector and the aftertreatment element.
- the purpose of the present invention is to provide an exhaust system of an internal combustion engine, said exhaust system overcoming the drawbacks described above and, in particular, being easy and inexpensive to produce.
- an exhaust system of an internal combustion engine is produced according to that set forth in the appended claims.
- number 1 indicates an overall exhaust system of a diesel" cycle internal combustion engine 2 (i.e. an engine that runs on diesel or similar types of fuel).
- the exhaust system 1 discharges the exhaust gas into the atmosphere and comprises an exhaust duct 3 which originates from an exhaust manifold 4 of the internal combustion engine 2.
- An oxidation catalyst 5 and a particulate filter 6 are arranged on the exhaust duct 3; in figure 1 the oxidation catalyst 5 and the particulate filter 6 are arranged in series inside a single common tubular container.
- an SCR (Selective Catalytic Reduction) system 7 for after-treatment of NO x (NO and NO 2 ) molecules is arranged on the exhaust duct 3 and downstream of the oxidation catalyst 5.
- the SCR catalytic system 7 can comprise a single SCR catalyst 7 as illustrated in figure 1 , or a series of catalysts (usually three) that together optimize the SCR function for after-treatment of NO x molecules.
- a feeder device 8 is connected to the exhaust duct 3, said device 8 being suitable to feed a reducing agent and in particular an aqueous urea solution (i.e. a solution of urea and water) into said exhaust duct 3.
- a reducing agent i.e. a solution of urea and water
- a aqueous urea solution i.e. a solution of urea and water
- the urea fed into said exhaust duct 3 spontaneously decomposes into isocyanic acid (HNCO) and ammonia (NH 3 ), said ammonia acting as a reducing agent in the catalytic system 7 to facilitate the conversion of the NO x molecules into nitrogen (N 2 ) and water (H 2 O).
- a static mixer 9 is arranged on the exhaust duct 3, in correspondence with the feeder device 3.
- the function of said mixer 9 is to generate turbulence in the exhaust gas in the exhaust duct 3 in order to prevent the localized thickening of the isocyanic acid (which forms during the decomposition of the urea) and thus prevent the polymerization of said isocyanic acid and improve the efficiency of the catalytic system 7 by distributing the ammonia more uniformly in the exhaust gas.
- the static mixer 9 is arranged downstream of the feeder device 8 (i.e. between the feeder device 8 and the catalytic system 7); alternatively, the static mixer 9 could be arranged upstream of the feeder device 8. According to an alternative embodiment which is not illustrated, two static mixers 9 could be provided and arranged respectively upstream and downstream of the feeder device 8.
- the static mixer 9 comprises a cylindrical tubular body 10, which has a central axis of symmetry 11 and two opposing annular edges 12, and two groups 13 of tabs 14 arranged on opposite sides of the tubular body 10.
- each group 13 the tabs 14 extend towards the outside of the tubular body 10 starting from a respective annular edge 12 of said tubular body 10, they are arranged at a distance from one another so as to leave an empty space 15 between two successive tabs 14, and slope towards the central axis of symmetry 11 so as to converge towards said central axis of symmetry 11.
- Each tab 14 of the static mixer 9 has substantially the shape of an isosceles trapezium with a longer base 16 arranged over the respective annular edge 12 of the tubular body 10 and a shorter base 17 which is free.
- the two groups 13 of tabs 14 are staggered so that each tab 14 of one group 13 is longitudinally aligned along the central axis of symmetry 11 with an empty space 15 between two successive tabs 14 of the other group 13.
- each tab 14 extends for the equivalent of the extension of an empty space 15 between two successive tabs 14; for example in the embodiment that is illustrated there are four tabs 14 each having an angular extension of 45° and alternating with four empty spaces 15 each having an angular extension of 45°.
- each tab 14 forms an angle ⁇ of between 30° and 60° and preferably of approximately 45° with the tubular body 10.
- the tubular body 10 preferably extends longitudinally along the central axis of symmetry 11 by at least 10 mm.
- each group 13 has four tabs 14 (and thus four empty spaces 15 arranged alternately with respect to the tabs 14); more generally, each group 13 is made up of between 3 and 6 tabs 14.
- the static mixer 9 only comprises a single group 13 of tabs 14 arranged along an annular edge 12 of the tubular body 10.
- the static mixer 9 comprises a number of fastening brackets 18, which extend parallel to the central axis of symmetry 11 starting from an annular edge 12 of the tubular body 10 and are arranged in correspondence with the empty space 15 between two successive tabs 14.
- the fastening brackets 18 are welded or riveted to a side wall of the exhaust duct 3 so that the static mixer 9 is integral with the exhaust duct 3; according to the embodiment in figures 2-4 in which the static mixer 9 is not provided with the fastening brackets 18, the static mixer 9 is fastened to the exhaust duct 3 by welding or riveting the tubular body 10 to the side wall of the exhaust duct 3.
- the static mixer 9 can be made by die-forming a flat metal sheet to define the tabs 14 (and, where applicable, the brackets 18), and then folding the die-formed sheet round a cylindrical core to give said die-formed sheet a tubular shape which is stabilized by means of welding or riveting; the tabs 14 are then folded towards the central axis of symmetry 11 to give them the shape described above.
- the static mixer 9 can be made by die-forming a tubular body of sheet metal to define the tabs 14 (and, where applicable, the brackets 18) and then folding the tabs 14 towards the central axis of symmetry 11 to give the tabs 14 the shape described above.
- the feeder device 8 is arranged upstream of the oxidation catalyst 5 to feed the fuel (for example diesel) into the exhaust duct 3, so that said fuel is burnt in the oxidation catalyst 5 to increase the temperature inside said oxidation catalyst 5 during a regeneration process of the particulate filter 6.
- the static mixer 9 is arranged upstream of the oxidation catalyst 5.
- the static mixer 9 described above has numerous advantages, in that it is simple and inexpensive to produce, is particularly robust (and thus has a long working life and very low risk of breaking) and above all it achieves an ideal balance between the opposing needs for effectiveness (i.e. to guarantee adequate mixing of the exhaust gas) and efficiency (i.e. to cause limited loss of pressure in the exhaust gas).
- the static mixer 9 described above achieves high effectiveness (i.e. it guarantees adequate mixing of the exhaust gas) and high efficiency (i.e. it causes limited loss of pressure in the exhaust gas).
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Dispersion Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Exhaust Gas After Treatment (AREA)
Description
- The present invention relates to an exhaust system of an internal combustion engine provided with an exhaust gas after-treatment arrangement.
- The present invention is advantageously intended for use in an exhaust system of an internal combustion engine provided with an exhaust gas after-treatment arrangement to which the following description specifically refers but without loss of generality.
- Next generation international standards limiting pollutant emissions by motor vehicles (the so-called "Euro5" and "Euro6" emission standards) will set very low thresholds for NOx emissions.
- Compliance with such limits is particularly critical especially for diesel engines; for this reason, a solution has been proposed which consists of providing exhaust systems of diesel engines with an additional NOx SCR (Selective Catalytic Reduction) system suitable to convert molecules of NOx (NO2 or NO) into nitrogen (N2), which is an inert gas, and water (H2O). It is difficult to convert NOx molecules into nitrogen (N) without the use of an adequate reducing agent. Ammonia (NH3) is generally used for this purpose. The reducing agent must be introduced into the exhaust system and upstream of the SCR catalyst in order to mix with the exhaust gas before it enters the SCR catalyst.
- However, storing ammonia inside a motor vehicle is not recommended for evident safety reasons relating to the fact that ammonia is toxic. Consequently, other solutions have been proposed which consist of storing and introducing an aqueous urea solution, as the urea is converted into ammonia due to the effect of the heat of the exhaust gas and also in part due to the catalytic effect.
- A problem associated with introducing an aqueous urea solution into the exhaust system is that the decomposition of the urea also results in the formation of isocyanic acid (HNCO), which tends to thicken and polymerize, building up on the inside walls of the exhaust system and resulting in the formation of solid deposits that are difficult to remove. To prevent the polymerization of the isocyanic acid generated from the decomposition of the urea, there have been proposals to arrange a mixer in the exhaust system close to the point in which the urea is introduced. Said mixer generates turbulence in the exhaust gas flow which prevents the localized thickening of the isocyanic acid and thus prevents the polymerization of said isocyanic acid. The presence of a mixer that generates turbulence in the exhaust gas flow immediately before said exhaust gas flow enters the SCR catalyst clearly also improves the efficiency of the SCR catalyst since it results in a more uniform distribution of the reducing agent (i.e. the ammonia) in the exhaust gas.
- Patent application
EP1514591A1 describes a mixer, which is arranged in an exhaust system of an internal combustion engine immediately upstream of an SCR catalyst into which the hot exhaust gas mixed with reducing agents is fed. Similarly, patent applicationsEP1022048A1 ,DE10060808A1 ,WO0107763A1 WO9913972A1 WO9905402A1 WO9905401A1 EP1748162A1 ,DE10248294A1 ,WO0009869A1 WO2005073524A1 ,WO0112301A1 EP0526392A1 ,EP0894523A1 describe exhaust systems provided with mixers arranged close to reducing agent feeder devices. - However, the known mixers of the type described above have the drawback of not achieving an ideal balance between the opposing needs for effectiveness (i.e. to guarantee adequate mixing of the exhaust gas) and efficiency (i.e. to limit loss of pressure in the exhaust gas). In other words, known mixers of the type described above are either low in effectiveness (i.e. they do not guarantee adequate mixing of the exhaust gas) or low in efficiency (i.e. they cause high losses of pressure in the exhaust gas).
-
WO2007127529A2 discloses an exhaust aftertreatment system including injection of chemical species; the system has a mixer provided by a stamped muffler flange and arranged in the exhaust pipe between the injector and the aftertreatment element. - The purpose of the present invention is to provide an exhaust system of an internal combustion engine, said exhaust system overcoming the drawbacks described above and, in particular, being easy and inexpensive to produce.
- According to the present invention an exhaust system of an internal combustion engine is produced according to that set forth in the appended claims.
- The present invention will now be described with reference to the attached drawings, illustrating some non-limiting embodiments thereon, in which:
-
figure 1 is a schematic view of an exhaust system of an internal combustion engine provided with an exhaust gas after-treatment arrangement and produced according to the present invention; and -
figure 2 is a schematic perspective view of a mixer of the exhaust system offigure 1 ; -
figure 3 is a front view of the mixer offigure 2 ; -
figure 4 is a side cross-sectional view along the line IV-IV of the mixer offigure 2 ; and -
figure 5 is a schematic perspective view of an alternative embodiment of the mixer offigure 2 ; - In
figure 1 , number 1 indicates an overall exhaust system of a diesel" cycle internal combustion engine 2 (i.e. an engine that runs on diesel or similar types of fuel). - The exhaust system 1 discharges the exhaust gas into the atmosphere and comprises an exhaust duct 3 which originates from an
exhaust manifold 4 of theinternal combustion engine 2. An oxidation catalyst 5 and a particulate filter 6 are arranged on the exhaust duct 3; infigure 1 the oxidation catalyst 5 and the particulate filter 6 are arranged in series inside a single common tubular container. - Moreover, an SCR (Selective Catalytic Reduction) system 7 for after-treatment of NOx (NO and NO2) molecules is arranged on the exhaust duct 3 and downstream of the oxidation catalyst 5. The SCR catalytic system 7 can comprise a single SCR catalyst 7 as illustrated in
figure 1 , or a series of catalysts (usually three) that together optimize the SCR function for after-treatment of NOx molecules. - Immediately upstream of the catalytic system 7, a feeder device 8 is connected to the exhaust duct 3, said device 8 being suitable to feed a reducing agent and in particular an aqueous urea solution (i.e. a solution of urea and water) into said exhaust duct 3. In use, due to the effect of the heat of the exhaust gas present in the exhaust duct 3, the urea fed into said exhaust duct 3 spontaneously decomposes into isocyanic acid (HNCO) and ammonia (NH3), said ammonia acting as a reducing agent in the catalytic system 7 to facilitate the conversion of the NOx molecules into nitrogen (N2) and water (H2O).
- A
static mixer 9 is arranged on the exhaust duct 3, in correspondence with the feeder device 3. The function of saidmixer 9 is to generate turbulence in the exhaust gas in the exhaust duct 3 in order to prevent the localized thickening of the isocyanic acid (which forms during the decomposition of the urea) and thus prevent the polymerization of said isocyanic acid and improve the efficiency of the catalytic system 7 by distributing the ammonia more uniformly in the exhaust gas. In the embodiment illustrated infigure 1 , thestatic mixer 9 is arranged downstream of the feeder device 8 (i.e. between the feeder device 8 and the catalytic system 7); alternatively, thestatic mixer 9 could be arranged upstream of the feeder device 8. According to an alternative embodiment which is not illustrated, twostatic mixers 9 could be provided and arranged respectively upstream and downstream of the feeder device 8. - As illustrated in
figures 2 ,3 and 4 , thestatic mixer 9 comprises a cylindricaltubular body 10, which has a central axis ofsymmetry 11 and two opposingannular edges 12, and twogroups 13 oftabs 14 arranged on opposite sides of thetubular body 10. - In each
group 13, thetabs 14 extend towards the outside of thetubular body 10 starting from a respectiveannular edge 12 of saidtubular body 10, they are arranged at a distance from one another so as to leave anempty space 15 between twosuccessive tabs 14, and slope towards the central axis ofsymmetry 11 so as to converge towards said central axis ofsymmetry 11. Eachtab 14 of thestatic mixer 9 has substantially the shape of an isosceles trapezium with alonger base 16 arranged over the respectiveannular edge 12 of thetubular body 10 and ashorter base 17 which is free. - The two
groups 13 oftabs 14 are staggered so that eachtab 14 of onegroup 13 is longitudinally aligned along the central axis ofsymmetry 11 with anempty space 15 between twosuccessive tabs 14 of theother group 13. - In correspondence with the respective
annular edge 12 of thetubular body 10 eachtab 14 extends for the equivalent of the extension of anempty space 15 between twosuccessive tabs 14; for example in the embodiment that is illustrated there are fourtabs 14 each having an angular extension of 45° and alternating with fourempty spaces 15 each having an angular extension of 45°. - The ratio between the diameter D of the circumference defined by the
longer bases 16 of thetabs 14 and the diameter d of the circumference defined by theshorter bases 17 of thetabs 14 is between 2 and 4 and preferably about 3. Moreover, eachtab 14 forms an angle α of between 30° and 60° and preferably of approximately 45° with thetubular body 10. Thetubular body 10 preferably extends longitudinally along the central axis ofsymmetry 11 by at least 10 mm. - In the preferred embodiment illustrated in the attached drawings, each
group 13 has four tabs 14 (and thus fourempty spaces 15 arranged alternately with respect to the tabs 14); more generally, eachgroup 13 is made up of between 3 and 6tabs 14. - According to an alternative embodiment which is not illustrated, the
static mixer 9 only comprises asingle group 13 oftabs 14 arranged along anannular edge 12 of thetubular body 10. - According to the alternative embodiment illustrated in
figure 5 , thestatic mixer 9 comprises a number offastening brackets 18, which extend parallel to the central axis ofsymmetry 11 starting from anannular edge 12 of thetubular body 10 and are arranged in correspondence with theempty space 15 between twosuccessive tabs 14. Thefastening brackets 18 are welded or riveted to a side wall of the exhaust duct 3 so that thestatic mixer 9 is integral with the exhaust duct 3; according to the embodiment infigures 2-4 in which thestatic mixer 9 is not provided with thefastening brackets 18, thestatic mixer 9 is fastened to the exhaust duct 3 by welding or riveting thetubular body 10 to the side wall of the exhaust duct 3. - The
static mixer 9 can be made by die-forming a flat metal sheet to define the tabs 14 (and, where applicable, the brackets 18), and then folding the die-formed sheet round a cylindrical core to give said die-formed sheet a tubular shape which is stabilized by means of welding or riveting; thetabs 14 are then folded towards the central axis ofsymmetry 11 to give them the shape described above. Alternatively, thestatic mixer 9 can be made by die-forming a tubular body of sheet metal to define the tabs 14 (and, where applicable, the brackets 18) and then folding thetabs 14 towards the central axis ofsymmetry 11 to give thetabs 14 the shape described above. - According to an alternative embodiment which is not illustrated, the feeder device 8 is arranged upstream of the oxidation catalyst 5 to feed the fuel (for example diesel) into the exhaust duct 3, so that said fuel is burnt in the oxidation catalyst 5 to increase the temperature inside said oxidation catalyst 5 during a regeneration process of the particulate filter 6. In this case, the
static mixer 9 is arranged upstream of the oxidation catalyst 5. - The
static mixer 9 described above has numerous advantages, in that it is simple and inexpensive to produce, is particularly robust (and thus has a long working life and very low risk of breaking) and above all it achieves an ideal balance between the opposing needs for effectiveness (i.e. to guarantee adequate mixing of the exhaust gas) and efficiency (i.e. to cause limited loss of pressure in the exhaust gas). In other words, thestatic mixer 9 described above achieves high effectiveness (i.e. it guarantees adequate mixing of the exhaust gas) and high efficiency (i.e. it causes limited loss of pressure in the exhaust gas).
Claims (14)
- Exhaust system (1) of an internal combustion engine (2); the exhaust system (1) comprises:an exhaust duct (3) which originates from an exhaust manifold (4) of the internal combustion engine (2);at least one catalytic system (7; 5) arranged on the exhaust duct (3);a feeder device (8), which is connected to the exhaust duct (3) immediately upstream of the catalytic system (7; 5) to feed an additive into said exhaust duct (3); andat least one static mixer (9), which is arranged on the exhaust duct (3) in correspondence with the feeder device (8) and comprises a tubular body (10) which has a central axis of symmetry and two opposing annular edges (12) and at least one group (13) of tabs (14), which extend towards the outside of the tubular body (10) starting from a respective annular edge (12) of said tubular body (10), are arranged at a distance from one another so as to leave an empty space (15) between two successive tabs (14), and slope towards the central axis of symmetry (11) so as to converge towards said central axis of symmetry (11);the exhaust system (1) being characterized in that:the static mixer (9) comprises two groups (13) of tabs (14) arranged along the two opposing annular edges (12) of the tubular body (10); andthe two groups (13) of tabs (14) are staggered so that each tab (14) of one group (13) is longitudinally aligned along the central axis of symmetry (11) with an empty space (15) between two successive tabs (14) of the other group (13).
- Exhaust system (1) according to claim 1, wherein each tab (14) of the static mixer (9) has substantially the shape of an isosceles trapezium having a longer base (16) arranged over the respective annular edge (12) of the tubular body (10) and a shorter base (17) which is free.
- Exhaust system (1) according to claim 2, wherein the ratio between the diameter of the circumference defined by the longer bases (16) of the tabs (14) and the diameter of the circumference defined by the shorter bases (17) of the tabs (14) is between 2 and 4.
- Exhaust system (1) according to claim 3, wherein the ratio between the diameter of the circumference defined by the longer bases (16) of the tabs (14) and the diameter of the circumference defined by the shorter bases (17) of the tabs (14) is approximately 3.
- Exhaust system (1) according to one of the claims from 1 to 4, wherein in correspondence with the respective annular edge (12) of the tubular body (10) each tab (14) extends for the equivalent of an empty space (15) between two successive tabs (14).
- Exhaust system (1) according to one of the claims from 1 to 5, wherein each tab (14) forms an angle of between 30° and 60° with the tubular body (10).
- Exhaust system (1) according to claim 6, wherein each tab (14) forms an angle of approximately 45° with the tubular body (10).
- Exhaust system (1) according to one of the claims from 1 to 7, wherein each group (13) has between 3 and 6 tabs (14).
- Exhaust system (1) according to claim 8, wherein each group (13) has 4 tabs (14).
- Exhaust system (1) according to one of the claims from 1 to 9, wherein the tubular body (10) extends longitudinally along the central axis of symmetry (11) by at least 10 mm.
- Exhaust system (1) according to one of the claims from 1 to 10, wherein the static mixer (9) comprises a number of fastening brackets (18), which extend parallel to the central axis of symmetry (11) starting from an annular edge (12) of the tubular body (10) and are arranged in correspondence with the empty space (15) between two successive tabs (14).
- Exhaust system (1) according to claim 11, wherein the fastening brackets (18) are welded or riveted to a side wall of the exhaust duct (3).
- Exhaust system (1) according to one of the claims from 1 to 12, wherein the catalytic system (7; 5) comprises:an oxidation catalyst (5) arranged on the exhaust duct (3); andan SCR catalytic system (7) arranged on the exhaust duct (3) downstream of the oxidation catalyst (5) and downstream of the feeder device (8).
- Exhaust system (1) according to one of the claims from 1 to 13, wherein the catalytic system (7; 5) comprises an oxidation catalyst (5) arranged on the exhaust duct (3) downstream of the feeder device (8).
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE602008002403T DE602008002403D1 (en) | 2008-02-12 | 2008-02-12 | Exhaust system of an internal combustion engine |
EP20080425083 EP2098697B2 (en) | 2008-02-12 | 2008-02-12 | Exhaust system of an internal combustion engine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP20080425083 EP2098697B2 (en) | 2008-02-12 | 2008-02-12 | Exhaust system of an internal combustion engine |
Publications (3)
Publication Number | Publication Date |
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EP2098697A1 EP2098697A1 (en) | 2009-09-09 |
EP2098697B1 true EP2098697B1 (en) | 2010-09-01 |
EP2098697B2 EP2098697B2 (en) | 2015-05-20 |
Family
ID=39638772
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP20080425083 Active EP2098697B2 (en) | 2008-02-12 | 2008-02-12 | Exhaust system of an internal combustion engine |
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EP (1) | EP2098697B2 (en) |
DE (1) | DE602008002403D1 (en) |
Families Citing this family (12)
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US8375709B2 (en) * | 2009-11-17 | 2013-02-19 | Tenneco Automotive Operating Company Inc. | Exhaust gas additive/treatment system and mixer for use therein |
US8359832B2 (en) | 2009-12-21 | 2013-01-29 | Caterpillar Inc. | SCR reductant mixer |
FR2956155B1 (en) * | 2010-02-05 | 2013-09-13 | Peugeot Citroen Automobiles Sa | EXHAUST LINE FOR AN INTERNAL COMBUSTION ENGINE |
US20110239631A1 (en) * | 2010-04-05 | 2011-10-06 | Caterpillar Inc. | Ring Reductant Mixer |
GB201100673D0 (en) | 2011-01-15 | 2011-03-02 | Statiflo Internat Ltd | Static mixer assembly |
ITBO20110533A1 (en) * | 2011-09-16 | 2013-03-17 | Magneti Marelli Spa | DISCHARGE SYSTEM OF AN INTERNAL COMBUSTION ENGINE PROVIDED WITH AN ADDITIVE INJECTION DEVICE |
EP2934732A1 (en) * | 2012-12-18 | 2015-10-28 | Invista Technologies S.à.r.l. | Processes for producing hydrogen cyanide using static mixer |
JP5787104B2 (en) * | 2013-02-21 | 2015-09-30 | トヨタ自動車株式会社 | Dispersion plate and dispersion device |
EP2910301B1 (en) | 2014-02-21 | 2016-08-31 | Modulo S.R.L. | Machine and method to produce urea mixers for exhaust devices of vehicles with internal-combustion engines |
DE102014205158A1 (en) * | 2014-03-19 | 2015-09-24 | Eberspächer Exhaust Technology GmbH & Co. KG | Mixer for an exhaust system |
DE102014222296A1 (en) | 2014-10-31 | 2016-05-04 | Eberspächer Exhaust Technology GmbH & Co. KG | Exhaust gas treatment device |
JP2021071054A (en) * | 2019-10-29 | 2021-05-06 | 株式会社豊田自動織機 | Urea water dispersion device and mounting structure for urea water dispersion device |
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DE19902207A1 (en) | 1999-01-21 | 2000-07-27 | Man Nutzfahrzeuge Ag | Process for metering a reducing agent, and device for carrying out the process |
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US20040265198A1 (en) * | 2003-06-30 | 2004-12-30 | Biswas Subodh Chandra | Power generation aftertreatment system |
EP1514591A1 (en) | 2003-09-15 | 2005-03-16 | J. Eberspächer GmbH & Co. KG | Hot gas flow channel, especially within an exhaust system of an internal combustion engine upstream of a catalyst |
DE102004004738A1 (en) | 2004-01-30 | 2005-08-18 | Robert Bosch Gmbh | Method and device for the after-treatment of an exhaust gas of an internal combustion engine |
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US7533520B2 (en) * | 2006-04-24 | 2009-05-19 | Fleetguard, Inc. | Exhaust aftertreatment mixer with stamped muffler flange |
-
2008
- 2008-02-12 DE DE602008002403T patent/DE602008002403D1/en active Active
- 2008-02-12 EP EP20080425083 patent/EP2098697B2/en active Active
Also Published As
Publication number | Publication date |
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EP2098697B2 (en) | 2015-05-20 |
EP2098697A1 (en) | 2009-09-09 |
DE602008002403D1 (en) | 2010-10-14 |
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