DE2452243A1 - PROCESS FOR REDUCING HARMFUL EXHAUST COMPONENTS IN THE EXHAUST GAS FROM AN COMBUSTION ENGINE - Google Patents

Description

November 4th P 8700

Nissan Motor Co., Ltd.

No. 2, Takara-machi, Kanagawa-ku, Yokohama City, Japan

Method for reducing harmful exhaust gas components in the exhaust gas of an internal combustion engine

The invention relates to a method for reducing the number of harmful exhaust gas components present in the exhaust gas of an internal combustion engine with an even number of combustion chambers before the exhaust gases escape into the free atmosphere.

The presence of harmful exhaust gas components in the exhaust gas of an internal combustion engine is mainly dependent on the air / fuel ratio of a combustible mixture supplied to the internal combustion engine. It is known that the formation of nitrogen oxides (NOx) can be reduced by using either a particularly high or low air / fuel ratio, since the greatest NOx concentration is produced in the region of the stoichiometric ratio. On the other hand, the concentrations of unburned fuel or hydrocarbons (HC) and carbon

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ni.onoir / 5-3 (COj with increasing air / fuel ratio from ρ v / '- 7 - x in other words "imsgacoriielst " when a lean ge? Tiisi-i: is used "Ss is, however, quite difficult to find the content of HC and CO in Äfogasss can only be brought to the low values required by the environmental protection regulations by using a very lean mixture. Therefore, the exhaust gas from an engine is often subjected to a second afterburning or to an afterburning that takes place in the exhaust gas system, whereby in general one thermal reactor is used, ma dis originally convert in the exhaust HC and CO Eesfcaadteile contained into harmless oxides. However, the reactivity of HC components and in particular from CO-Bestandteilan with existing in small amounts of air and / or at relatively low temperatures extremely bad If post-combustion is planned, then a rich, combustible mixture is more favorable, as there are high EC and CO concentrations in the A bgas can be detected, which ensure complete afterburning, while the NOx concentration itself decreases, as has already been stated. In practice, however, the use of a rich mixture is rather disadvantageous because it also leads to uneconomical fuel consumption.

The invention is therefore directed to a method su create by which the in the exhaust gas a typical Internal combustion engine with a straight Brennkammersahi contained harmful exhaust gas components are significantly reduced before the exhaust gases escape into the free atmosphere the fuel consumption should not increase substantially.

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The invention is that the combustion chambers to one a first and a second group are combined, each group comprising one half of the total number of combustion chambers, that the first or second combustion chamber group has a first air-fuel mixture, its air / fuel ratio is significantly below the stoichiometric ratio, or a second air-fuel mixture whose air / Fuel ratio is substantially above the stoichiometric ratio, are supplied to the engine in such a way is operated that each combustion chamber of the first combustion chamber group has a first exhaust gas flow and in each case a specific one Combustion chamber of the second combustion chamber group simultaneously generate a second exhaust gas flow, and that the first and the second Exhaust gas stream are mixed together in an exhaust system of the engine, so that the unburned contained in the exhaust gas HC and CO components with that in the second Excess air present in the exhaust gas flow react. For mixing the exhaust gas and for the subsequent reactions a thermal reactor is preferably provided.

The NOx concentration can be reduced significantly because the air / fuel ratio of both the first mixture as well as the second mixture deviates significantly from the stoichiometric ratio. The first group of Combustion chambers or cylinders emit a first exhaust gas flow, which has relatively large HC and CO proportions, while the second group emits a second exhaust gas stream containing a relatively large proportion of hot air. This yourself differently composed two exhaust gas streams are always expelled from the engine at the same time, so that they are in the exhaust system can be easily mixed with each other, with different oxidation reactions at relative high temperatures take place. The HC and CO components can therefore be almost completely removed from the exhaust gases, before the exhaust gases escape into the open atmosphere.

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2 A 5 2 2 Λ

Further features, details and advantages of the invention result from the following description of exemplary embodiments with reference to the drawing. Show in it:

Fig.1 is a schematic plan view of a partial 6-cylinder engine shown in section and a thermal reactor according to a first embodiment for carrying out the method according to the invention ;

2 shows a plan view of part of an exhaust gas outlet pipe for the thermal reactor according to Figure 1;

FIG. 3 is a schematic plan view similar to FIG second preferred device for performing the method according to the invention and

Fig. 4 is a top view of a partially shown in section 4-cylinder engine and a thermal reactor according to a third preferred embodiment for carrying out the method according to the invention.

1 shows a 6-cylinder engine 10 which is equipped with two carburetors 20 and 21. In which 6-cylinder engine 10 form three cylinders or combustion chambers 11, 12 and 13, which in the drawing are on the left of the engine 10 are shown, a first cylinder group, and the remaining three cylinders 14, 15 and 16, which are in the

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Drawing shown on the right side of the engine form a second group of cylinders. During the first carburetor 20 supplies the first cylinder group 11 to 13 with a relatively rich air-fuel mixture, the one significantly below the stoichiometric ratio has a lying air / fuel ratio, e.g. about 12/1, the second carburetor 21 supplies the second cylinder group 14 to 16 with a relatively lean mixture, the Air / fuel ratio is significantly higher than the stoichiometric ratio, e.g. 18/1. On the other hand, they could Carburetors 20 and 21 can also be replaced by a conventional fuel injection system, which is not shown in the drawing is. According to the invention, the engine 10 is designed such that each cylinder 11, 12 or 13 of the first Cylinder group at the same time as a specific cylinder 14, 15 or 16 of the second cylinder group is ignited. In the embodiment shown in FIG the cylinders 11 and 16 are fired first, then the cylinders 13 and 14 and then the cylinders 12 and 15. The Ignition distribution, valve control and design of the not shown crankshaft of the engine 10 are chosen so that of the cylinders 11 to 16 each two certain Cylinders are ignited per unit of time in the sequence described above.

The engine 10 is equipped with two exhaust pipes, namely with a first exhaust pipe 30 and a second exhaust pipe 31, which over the outlet openings for the exhaust gas 41 to 46 of the respective cylinders 11 to connected on the one hand to the first cylinder group 11 to 13 and on the other hand to the second cylinder group 14 to 16

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Silicic The exhaust pipes. 30 and 31 are connected by a thermal «;. ': Rector 50 Hiitainande-r, into which they flow with their inlets 51 and 52, respectively, " Dar Innenrauia 53 "which serves as Rfeaktionskaxnmsr " is precautionary cylindrical nüsgeblldet, and the first inlet 51 iM © ia AusIaS 54 are arranged at one end 55 of the interior space at the garage overlying end 56. The second inlet 52, which is arranged in a central section of the reaction chamber 53., mÜRj- et does not directly enter the reaction chamber 53, but is connected to a pipe 5? "The pipe 57 ex ° - stretches to the end 55, so that an open end 58 of the pipe is located in the vicinity of the first inlet 51 open end 58 is located, i / Orsugsweise in the longitudinal axis of the reaction chamber 53 'and in which in. the open end 58 adjoining region is arranged a swirl plate 59 in the tube 57.

The combustion cycle takes place while the engine is in operation and extension cycle of the cylinder pair 11 and 16 at the same time, so that the exhaust gas flows into the two exhaust pipes 30 and 31 at the same time. Since the cylinders 11 and 16 with a rich bsw, a lean air-fuel mixture a first exhaust gas flow flowing into the first exhaust gas line 30 contains relatively high amounts of HC and CO ^ while a second in the second exhaust line 31 flowing Exhaust gas stream contains a relatively large amount of hot air. During the first exhaust gas flow through the first inlet 51 flows into the reaction chamber 53, shortly thereafter the second exhaust gas stream is shaped through the opening 58 of the tube 57 a swirl flow is blown into the reaction chamber 53. Then the first and the second exhaust gas stream meet

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and mix, causing a violent afterburn the excess air of the second exhaust gas stream with the HC and CO components contained in the first exhaust gas stream takes place. The reactions progress as the exhaust gases mix together towards the opposite end 56 of the reaction chamber 53 flow, and are finished before the exhaust gases exit through outlet 54 of reactor 50.

the initial mixing of the first and second exhaust gas streams to promote, the first inlet 51 is preferably arranged such that the first exhaust gas flow tangentially in the cylindrical reaction chamber 53 enters, so that a swirl flow is generated which has the same direction like the swirl flow of the second exhaust gas flow, which is generated as a result of the swirl plate 59. The outlet 58 of the tube 57 could also be designed in accordance with the embodiment shown in FIG. In this case it is the swirl plate 59 according to FIG. 1 is omitted, and in the vicinity of the closed end 58b of the pipe 57 there are many very small holes 58a arranged in the pipe wall. The second Exhaust gas stream is injected through the very small holes 58a and mixes with the first exhaust gas stream, which the pipe 57 flows around.

After the ignition of the cylinders 11 and 16, another pair of cylinders is ignited 13 and 14 simultaneously, and then the ignition follows the last pair of cylinders 12 and 15, wherein the above-described reactions are repeated in the thermal reactor 50th

Since in the thermal reactor 50 relatively large HC and CO

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Components are burned when the air exiting with the second exhaust gas flow is still considerably high Has temperature, the reactions take place in the reaction chamber 53 at considerably high temperatures and lead to an almost complete elimination of the HC and HC substances originally contained in the first and second exhaust gas streams CO components. Since the NOx concentration is reduced by the use of the first and second air-fuel mixture, both of which differ significantly from the stoichiometric mixture, is naturally reduced, the exhaust gas exiting the thermal reactor 50 is remarkably pure.

Of course, the assignment of the first or bold Air-fuel mixture to the first cylinder group 11 to 13 and the assignment of the second or lean mixture to the second cylinder group 14 to 16 can also be reversed, with the same result is achieved. In addition, it should be noted that the implementation of the method according to the invention not necessarily the use of a thermal reactor 50 but the first and second exhaust gas streams cannot be connected to all cylinders 11 to 16 either shown exhaust manifold mixed together, are and react there.

In Figure 1 it is also shown that the first exhaust pipe 30 is preferably equipped with additional or auxiliary air nozzles 61, 62 and 63, which are located in the vicinity of the exhaust gas outlet openings 41, 42 and 43 are arranged. The additional air nozzles 61 to 63 are connected to an air line 64, which is monitored by a solenoid valve 65, the solenoid valve 65 is normally closed and by a Control device 66 is moved into the open position,

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which in turn affects the engine load and. responds to the position of a switch. When the engine 10 is idling or running at a relatively low load, then the temperature of the first exhaust gas stream is so low that it is suitable for initiation of the reactions in the thermal reactor 50 is insufficient. So if in such a case the If the load of the motor 10 falls below a certain value, the control device 66 responds and actuates the solenoid valve 65, so that additional air is passed into the first exhaust pipe 30. This burns part of the first Exhaust gas flow contained HC components within the exhaust pipe 30, so that the exhaust gas temperature rises significantly before the exhaust gas flow reaches the thermal reactor 50.

To carry out the method according to the invention, either the grouping of the cylinders 11 to 16 or the design of the thermal reactor 50 are changed. at In the second embodiment shown in Figure 3, the three cylinders 11, 13 and 15 form the first group of cylinders, while the three cylinders 12, 14 and 16 form the second group of cylinders. In other words, the cylinders of the first and second cylinder groups are arranged alternately. The cylinders of the three cylinder pairs 11-12, I3-I4 and 15-16 are in the order described accordingly ignited at the same time. The ignition distribution, valve timing and configuration of the crankshaft of the engine 10a differ from the ignition distribution, valve control and configuration of the crankshaft of the engine 10 according to FIG the operation of the engine with this appropriate grouping and firing order is made possible. An exhaust pipe 33

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serves for the common discharge of the exhaust gases emerging from all cylinders 11 to 16. It's a thermal one Reactor 50a provided, which has a substantially cylindrical reaction chamber 53, which in turn has an in near one end 55 arranged inlet 51 and in the Has outlet 54 disposed near the opposite end 56. In this embodiment one begins Mixing of the emerging from the cylinder pair 11-12 first exhaust gas stream with that from the cylinder pair 15-16 or 13-14 exiting second exhaust gas flow in the exhaust line 33, while then the flow in the Reaction camper 53 takes place. Then the combustion reactions run, as described in connection with Fig. 1, and are completed in the reaction chamber 53. The embodiment shown in FIG. 3 is one of them simplified design of the exhaust pipe 33 and the thermal Reactor 50a marked.

FIG. 4 shows a further exemplary embodiment of a device which is used to carry out the method according to the invention and has a 4-cylinder engine 10b. While two cylinders 11b and 14b are supplied with a rich air-fuel mixture, the remaining two cylinders 12b and 13b, which are arranged between the cylinders 11b and 14b, are supplied with a lean mixture. Of course, the rich and lean mixture can also be fed in in the opposite way. The engine 10b is designed in such a way that first the cylinders 11b and 12b and then the cylinders 13b and 14b are ignited at the same time. An exhaust pipe 34, which has an outlet 35, is connected to all cylinders 11b to 14b. The interior of the exhaust pipe 34 is by means of a separating

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wall 36 is preferably divided into two sections so that a rapid exit of the exhaust gases through the outlet 35 is made possible through it. For example, the thermal Reactor 50a be connected. However, the Figure 4 shows another thermal reactor 70, which consists of a cylindrical Inner housing 71 and a cylindrical outer housing 72, wherein in the inner housing 71 a Reaction chamber 73 and a space 74 between the two housings 71 and 72 are arranged. The two cylindrical Housings 71 and 72 are arranged essentially coaxially with one another. The reaction chamber 73 is with a Inlet 75, which is arranged in the middle of the wall of the inner housing 71, to the outlet 35 of the exhaust pipe connected. The inlet 75 extends through the space 74 and through the wall of the outer housing 72, where he Compared to room 74 is complete. Several holes 76 in the wall of the inner housing 71 on both Ends 77 and are arranged in peripheral parts in the region of these ends, provide a connection between the Reaction chamber 73 and the space 74 ago. In the reaction chamber 73 there are preferably two intermediate walls 78 at between the inlet 75 and the ends 77 located points which the reaction chamber 73 in three sections subdivide. A plurality of through bores 79 arranged in the intermediate walls 78 connect the one formed in this way middle section 73a with the remaining sections of the reaction chamber 73. The outer housing 72 has an outlet opening 80 in the middle of its wall.

While the engine is running, the two under-

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differently composed exhaust gas flows in the exhaust pipe 34, if for example the two cylinders 11b and 12b perform the same work cycle. The two exhaust gas streams mix as they pass through the inlet 75 when in the middle section 73a. the reaction chamber 73 flow in. Through the from the partitions Caused delay in the exhaust gas flow is a thorough mixing of the two exhaust gas flows, so that stable combustion is achieved in the central portion 73a. The combustion reactions move with it the subsequent exhaust gas mixture flow from the middle one Section 73a through the through holes 79 to the side portions of the reaction chamber 73. Then flow the still burning exhaust gases or the exhaust gases already completely burned through the holes 76 into the room and around the inner housing to the center of the thermal reactor 70 where the exit port 80 is located.

Such a long flow path provided in the thermal reactor 70 causes them to mix with one another Exhaust gases remain in the thermal reactor long enough so that there is virtually complete oxidation the HC and CO components originally contained in the exhaust gases is achieved. In addition to a long reaction time, the bypassing of the hot exhaust gases around the Inner housing 71 that the reaction chamber 73 on a high temperature is maintained so that the combustion reactions can be initiated easily and uniformly expire.

The ones serving for the supply of additional air and already

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Additional air nozzles 61 and 62 described can be in the exhaust pipe 34 in the vicinity of the exhaust gas outlet openings 41b and 44b of the cylinders 11b and 14b supplied with the rich mixture.

Of course, the arrangement of the cylinders of the 4-cylinder engine, which according to the invention with bold and lean mixtures are supplied, either as with that Embodiment according to Figure 1 or the embodiment according to Figure 3 can be selected. It should also be noted that each thermal reactor 50, 50a and 70 in conjunction with any one designed in accordance with the invention Motor can be used with the associated corresponding exhaust pipe. In addition, either the thermal reactor 50 or 50a like thermal reactor 70 with one outer casing and one between the two Housings arranged space be equipped.

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Claims (8)

Claims 1. Method for reducing in the exhaust gas of an internal combustion engine with an even number of combustion chambers harmful exhaust gas components before the exhaust gases escape into the open atmosphere, thereby characterized / that the combustion chambers (11,12,13,14,15,16,11b, 12b, 13b, 14b) to a first and a second group, each group comprising one half of the total number of combustion chambers that of the first or »second combustion chamber group a first air-fuel mixture, its air-fuel ratio is significantly below the stoichiometric ratio, or a second air-fuel mixture, its air / fuel ratio is essential is above the stoichiometric ratio, are supplied that the engine (10,10a, 10b) is operated in such a way that each combustion chamber of the first combustion chamber group a first exhaust gas flow and in each case a specific combustion chamber of the second combustion chamber group simultaneously generate a second exhaust gas stream, and that the first and the second exhaust gas stream in an exhaust system (50,50a, 70) of the engine are mixed together so that the contained in the exhaust gas unburned fuel components and carbon monoxide react with the excess air present in the second exhaust gas stream. 509820/0757 2. The method according to claim 1, characterized in that the first and the second exhaust gas stream react with one another _{in a thermal reactor (50.5Oa x VO).} 3. The method according to claim 2, characterized in that the first and the second Waste gas streams are introduced separately from one another into the thermal reactor (50,5Oa, 70) and that at least one exhaust gas flow is set in a rotary motion upon entry into the thermal reactor. 4. The method according to claim 1 or 2, characterized in that the first and the second exhaust gas stream at least partially with one another before it enters the thermal reactor (50a, 70) be mixed. 5. The method according to any one of claims 1 to 4, characterized in that the first and the second exhaust gas flow with each other in a thermal Reactor (70) react, which is a reaction chamber arranged in a cylindrical inner housing (71) (73), the cylindrical inner housing from a cylindrical outer housing (72) under Formation of a space (74) arranged between the two housings is enclosed, and that from the 1st gas stream and the 2nd gas stream formed mixture is then passed through the space, so that the reaction is complete and the reaction chamber is kept at a high temperature level. 509820/0757 6. Method of reducing in the exhaust gas of an in-line 6-cylinder engine existing harmful exhaust gas components before escaping into the open atmosphere, thereby characterized in that a first air-fuel mixture with an air / fuel ratio, which is substantially below the stoichiometric ratio, fed to a first cylinder group which consists of three cylinders No. 1, No. 2 and No. 3, the cylinders being arranged one behind the other 'and are numbered starting from an outer cylinder that a second air-fuel mixture with an air / fuel ratio that is significantly above the stoichiometric ratio, one is fed to the second cylinder group, which consists of the three remaining cylinders No. 4, No. 5 and No. 6, The cylinders are also arranged one behind the other and numbered starting from cylinder number 3 are that the engine (10) is operated in such a way that two cylinders of three cylinder pairs No. 1 and 6, no.3 and 4 and no.2 and 5 exhaust gases at the same time eject, the three pairs of cylinders working in the sequence described, and that the exhaust gas each Cylinder of the first cylinder group and the exhaust gas emitted at the same time from a corresponding cylinder the second group of cylinders together in a thermal reactor (50). be mixed up in that Exhaust system of the engine is arranged. 7. Method of reducing in the exhaust gas of an in-line 6-cylinder engine existing harmful exhaust gas components before escaping into the open atmosphere, 509820/0757 characterized in that a first air-fuel mixture with an air / fuel ratio, which is substantially below the stoichiometric ratio, fed to a first cylinder group which consists of three cylinders No. 1, No. 3 and No. 5, that a second air-fuel mixture with an air / fuel ratio that is significantly above the stoichiometric ratio, one the second cylinder group is fed, which consists of the three remaining cylinders No. 2, No. 4 and No. 6, the individual cylinders of the first cylinder group and the second cylinder group alternating are arranged that the engine (TOa) is operated such that two cylinders of three cylinder pairs No. 1 and 2, No. 5 and 6 and No. 3 and 4 simultaneously expel exhaust gases, with the three pairs of cylinders work in the sequence described, and that the exhaust gas of each cylinder of the first cylinder group and the simultaneously emitted exhaust gas of a corresponding cylinder of the second cylinder group with one another a thermal reactor (50a) arranged in the exhaust system of the engine. 8. Method of reducing in the exhaust gas of a 4-cylinder engine existing harmful exhaust gas components before escaping into the open atmosphere, thereby characterized in that a first air-fuel mixture with an air / fuel ratio, which is substantially below the stoichiometric ratio, fed to a first cylinder group which consists of two cylinders # 1 and # 4, 509820/0757 The cylinders are arranged at both ends of the cylinder row so that a second air-force * substance mixture with an air / fuel ratio, which is significantly above the stoichiometric ratio, is fed to a second group of cylinders, which consists of the two remaining cylinders # 2 and # 3 that the engine (10b) is operated is that the two respective cylinders of the two cylinder pairs No. 1 and 2 and No. 3 and 4 at the same time Eject exhaust gases, the two pairs of cylinders working in the sequence described, and that the exhaust gas of each cylinder of the first cylinder group and the exhaust gas of a corresponding one emitted simultaneously Cylinders of the second group of cylinders are mixed with one another in a thermal reactor (70), the is arranged in the exhaust system of the engine. 509820/0 7 57