EP1151184A1

EP1151184A1 - Exhaust system with at least one baffle plate

Info

Publication number: EP1151184A1
Application number: EP00907462A
Authority: EP
Inventors: Wolfgang Maus
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH
Current assignee: Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 1999-02-08
Filing date: 2000-01-11
Publication date: 2001-11-07
Anticipated expiration: 2020-01-11
Also published as: JP4526190B2; DE50003635D1; AU2904100A; DE19905032A1; US20020017097A1; WO2000047878A1; EP1151184B1; MY122685A; JP2002536589A; US6487854B2; RU2227834C2

Abstract

The invention relates to an exhaust system (1) comprising an exhaust manifold (2) for merging the exhaust-gas streams (11, 12, 13, 14) arriving from two or more cylinders of an internal combustion engine. The manifold (2) comprises an exhaust cross-section (9) downstream of which a jacket tube (3) is connected which houses a honeycomb (7). Between the exhaust cross-section (15) and the honeycomb (7) a chamber (10) is positioned through which the exhaust gas is able to flow and in which at least one first baffle plate (8) for deflecting at least part of the exhaust-gas streams (11, 12, 13, 14) is arranged. In addition to the manifold (2) and honeycomb (7) the invention also relates to a method for subjecting a honeycomb (7) to exhaust-gas streams (11, 12, 13, 14). At least a part of the exhaust-gas streams (11, 12, 13, 14) arrives at the honeycomb (7) from different directions and before striking the honeycomb (7) is deflected by means of at least a first baffle plate (8) in such a way that said exhaust-gas streams at least partly flow in a direction opposite to the direction of flow of the exhaust gas streams (11, 12, 13, 14) so that their arrival at the honeycomb (7) is delayed.

Description

Exhaust system with at least one guide surface

The present invention relates to an exhaust system with a collector for merging exhaust gas flows from two or more cylinders of an internal combustion engine, the collector having an outlet cross section, behind which a jacket pipe connects, in which a honeycomb body is arranged. Furthermore, a collector, a honeycomb body and a method for the application of exhaust gas flows to a honeycomb body are dealt with.

Legal requirements require that the cold start behavior of internal combustion engines be improved with regard to their exhaust emissions. For this purpose it is known to install a first catalytic converter close to the engine, e.g. to be provided close behind an elbow. Due to the high temperatures behind the manifold, this causes the catalytic converter arranged behind it to heat up quickly, but there it is also exposed to high thermal and mechanical alternating loads due to the pulsating exhaust gas flows.

The object of the present invention is to improve the emission behavior of an internal combustion engine, in particular in the cold start phase, in particular the service life of a honeycomb body used close to the engine to be extended.

This object is achieved by an exhaust system with the features according to claim 1, by a collector with the features according to claim 8, by a honeycomb body with the features according to claim 9 and by a method with the features of claim 11. Advantageous refinements and developments are specified in the respective dependent claims. The exhaust system according to the invention with a collector for merging exhaust gas flows from two or more cylinders of an internal combustion engine, the collector having an outlet cross section, behind which a jacket pipe connects, in which a honeycomb body is arranged, is characterized in that between the outlet cross section and the Honeycomb body is a space to be flowed through, in which at least one first guide surface is arranged for deflecting at least some of the exhaust gas flows.

Such a first guide surface delays the impact of the individual exhaust gas flows on the upstream end face of the honeycomb body. The swirling of the exhaust gas streams leads to improved mixing of a total exhaust gas stream supplied to the honeycomb body, which in particular improves the subsequent catalytic reaction. The measuring accuracy of a lambda probe for measuring the oxygen content, which may be arranged in the collecting space or behind it, is increased, since the somewhat uneven

Composition of the individual exhaust gas flows is at least partially compensated. Since the exhaust gas flows flow into the collector in the form of a pulsation flow, the first guide surface absorbs and reduces a pressure gradient.

The downstream honeycomb body is relieved of this pressure gradient. Damage due to the pulsation flow as it lasts for a long time

Operating period could occur, are avoided in an advantageous manner.

It is also advantageous if the first guide surface is designed such that the exhaust gas flows are deflected in front of the honeycomb body. The deflection, which means a substantial change in the original flow direction of the exhaust gas streams, in turn delays their impact on the honeycomb body, so that, in particular, there is already an interaction with the next exhaust gas pulse from another exhaust gas line in order to equalize the pressure. In particular, a negative pressure after the pressure pulse is also established in the other cylinders. On the other hand, it allows by occurring Vortex formation in turn leads to good mixing of the fluid flow. A further development of the first guide surface provides that it is designed so that the exhaust gas flows flow back at least in part. This means that the exhaust gas flows are at least partially redirected in the direction from which they come in. The first guide surface is preferably arranged such that it is at least partially opposite the exhaust gas flows flowing in the room. A further development provides that the first guide surface is arranged so that a direct flow of the exhaust gas flows to the honeycomb body is at least partially blocked.

On the one hand, this leads to the fact that a linear action on the end face of the honeycomb body is hindered, preferably even completely prevented. If the flow path is at least partially blocked, the pressure gradient is reduced at least to such an extent that damage to the honeycomb body that may occur is prevented over a longer operating period. In addition, there are mixing effects between the individual exhaust gas flows. Chemical reactions as well as temperature adjustments can be achieved by this mixing. Delayed pressure differences in the individual exhaust gas streams can be compensated for in such a way that, after swirling, a uniform total exhaust gas stream hits the end face of the honeycomb body.

An embodiment of the first guide surface provides, for example, to use a guide plate for this. The baffle must be able to absorb occurring temperature and pressure differences. In particular, the first guide surface is designed such that it reduces the free cross section behind the outlet cross section, which is then followed by the free cross section of the casing tube. The first guide surface is therefore preferably designed as a type of diaphragm. Alternative and / or cumulative designs of a first guide surface provide that this is uniformly and / or unevenly, partially or completely distributed holes and / or cutouts on the lateral outer edge and / or at least one edge opening and / or at least one curvature on at least one of their surfaces having.

Between the outlet cross section and the first guide surface, a vortex space is preferably formed as a reaction space. There is enough space in it to ensure, for example, that the individual exhaust gas flows can be mixed. Furthermore, this vortex space also serves in a certain way as a calming space for the total exhaust gas flow that finally occurs on the end face of the honeycomb body. A suitable dimensioning of the swirl space can be used to set the manner in which mixing takes place after swirling through the guide surface. The shape of the swirl chamber also determines the manner in which pressure gradients of the individual exhaust gas flows act against one another and can ultimately be equalized. The swirl chamber also serves to form a uniform temperature distribution within the total exhaust gas flow ultimately striking the honeycomb body.

It is preferred if the first guide surface is arranged closer to the outlet cross section than to the honeycomb body. On the one hand, the guide surface catches a pressure gradient much earlier. On the other hand, it is possible to distribute a resulting total flow behind the guide surface from the different exhaust gas streams over the adjoining free cross-section of the jacket tube so that the entire front surface of the honeycomb body is flowed evenly over its cross-section.

In particular, the formation of back vortices behind the guide surface can interact with a corresponding design of the flow surface be avoided. The same applies to the avoidance of areas in which a detached flow and thereby areas arise in which parts of the exhaust gas flow remain for a certain period of time in comparison with the rest of the flow. If a guide surface is not sufficient to achieve the advantages described, it is proposed to arrange a second guide surface in the space to be flowed through between the first guide surface and the honeycomb body.

The collector according to the invention is characterized in that at least one first guide surface is part of the collector. If this is a casting, for example, the flow area is cast in one operation together with the other parts of the collector.

The honeycomb body according to the invention in a casing pipe for an exhaust system is characterized in that at least one first guide surface is part of the casing pipe. This can be done, for example, by appropriate crimping or the like during manufacture of the casing tube.

Alternative embodiments provide that the guide surface for the exhaust system is arranged as an interchangeable component between the collector and the casing pipe. This can be installed, for example, as an insert in the collector or in the casing tube. The guide surface between the collector and the jacket tube can also be flanged.

As a result of the proposed arrangements of at least one guide surface on an edge of the flow path to the honeycomb body, it is possible in an advantageous manner to keep a central cross section of the space to be flowed behind the guide surface, but at the same time also to offer the inflow of the exhaust gas flows a corresponding counter surface for swirling.

The inventive method for applying a honeycomb body with exhaust gas flows, which at least partially from different directions get to the honeycomb body, is characterized in that the exhaust gas streams are deflected by at least one first guide surface before they strike the honeycomb body so that they flow at least partially in a direction opposite to the exhaust gas streams and thus hit the honeycomb body with a delay. Before striking the honeycomb body, the individual exhaust gas flows are deflected in such a way that they flow at least partially in the opposite direction, thereby mixing with one another and only then striking the honeycomb body. This method is particularly preferred if the exhaust gas flows flow to the honeycomb body in a pressure-pulsating manner. The method is also very useful if the individual exhaust gas streams flow towards the honeycomb body at different times.

In order to further improve the emission behavior of an internal combustion engine, particularly in the cold start phase, it is proposed that the exhaust gas streams deflected and swirled by the first guide surface flow through a second guide surface, whereby in addition to the described advantages, the entire end face of the honeycomb body in particular is evenly more uniform over its surface Cross-section is flown.

Further advantages and features of the invention are explained in more detail with reference to the following drawing, which, combined with one another and with the features mentioned above, result in additional advantageous developments. The drawing shows a preferred field of application of the invention. In addition to the use of the exhaust system, the collector, the honeycomb body and the method in an exhaust line of an internal combustion engine, the invention can also be used in particular where several individual fluid streams meet from different directions and immediately afterwards encounter a honeycomb body with a catalytically active coating, special features Advantages of the invention result for fluid streams which on the one hand have pressure gradients, staggered in time, in particular flow into one another, react chemically or have temperature gradients within the fluid flow or between fluid flows.

Show it:

1 shows an exhaust system with a collector and a directly connected honeycomb body in a perspective view;

FIG. 2 shows a schematic view of the exhaust system according to FIG. 1;

3 shows a first exemplary embodiment of a guide surface in the manner of an aperture;

4 shows a second exemplary embodiment of a guide surface which is curved;

5 shows a third exemplary embodiment of a guide surface which is curved and has a cutout at its edge; and

6 shows a cross section through the guide surface according to FIG. 5.

1 shows a preferred area of application of an exhaust system 1 with a collector 2 for merging exhaust gas flows from two or more cylinders of an internal combustion engine, not shown, in particular four exhaust gas flows of a four-cylinder engine. Immediately behind the collector 2 is a jacket tube 3, in which a honeycomb body 7 is arranged as a starting catalyst. As can be seen from this figure, the exhaust system 1 is preferably constructed so that first flanges 4 each lead to the individual cylinders of the internal combustion engine, while a second flange 5 in the flow direction through the collector 2 behind the casing pipe 3 for connection, for example, to an exhaust line, not shown leads towards a silencer. The exhaust system 1 forms a single component that can be installed as a whole in the exhaust line of the internal combustion engine. It is expedient if the exhaust system 1 has a parting plane 6, so that the collector 2 and the casing tube 3 can be separated from one another again, for example for exchanging the starting catalytic converter.

FIG. 2 shows a schematic view of the exhaust system 1 from FIG. 1. Objects of the same type have the same reference numbers. Between the collector 2 and the honeycomb body 7 as the starting catalyst, a first guide surface 8 is arranged in a space 10 to be flowed through. From the respective individual cylinders of the internal combustion engine, a first exhaust gas flow 11, a second exhaust gas flow 12, a third exhaust gas flow 13 and a fourth exhaust gas flow 14, each indicated by an arrow, pass through an outlet cross-section 9 of the collector 2, here indicated by dashed lines in FIG. 2 a swirl chamber 15. The individual exhaust gas flows 11, 12, 13, 14 can lead to a selective application of an end face 16 of the honeycomb body 7. However, the first guide surface 8 is arranged in the space 10 to be flowed through in such a way that the individual exhaust gas flows 11, 12, 13, 14 are at least partially swirled and deflected. For example, the first exhaust gas flow 11 partially rebounds from the first guide surface 8 and flows against the adjacent second exhaust gas flow 12. This results in the mixing of these two exhaust gas flows 11, 12. This can be used in particular due to the pressure pulsations in the exhaust system 1 by the acting cylinder movements. By suitable arrangement and design of the first guide surface 8 in the space 10 to be flowed through, the mixing of the exhaust gas flows 11, 12, 13, 14 can be optimized in particular so that there is an increased dwell time in the space 10 to be flowed through for a wide load range of the engine. The result of this is that, for example, on the one hand, the first exhaust gas stream 11 itself is mixed again due to the swirling, but at the same time mixing is also effected with the adjacent second exhaust gas stream 12. Because of this, reactions and conversions in the exhaust gas mixture that have not yet been carried out are excited, temperature differences are compensated for, and a uniform volume flow flows as a resultant gas flow onto the honeycomb body 7, causes. It is therefore preferred that the first guide surface 8 is at a greater distance from the end face 16 of the honeycomb body 7 than from the outlet cross section 9 of the collector 2. The distance A between the end face 16 of the honeycomb body 7 and the outlet cross section 9 is chosen in particular so that a resulting Total exhaust gas flow 17, shown here as a fanning-out multiple arrow, at least largely flows onto the entire end face 16 of the honeycomb body 7. Mixing due to swirling and backflow of the individual exhaust gas streams 11, 12, 13, 14 also reduces a selectively increased, thermally induced voltage of the honeycomb body 7 in the region of the end face 16, which in turn results in the conversion of previously unburned hydrocarbons to a yet to be carried out Uniformization of the temperature load of the honeycomb body 7 leads.

Fig. 3 shows a first exemplary embodiment of a guide surface 8, which has the shape of an annular aperture. The aperture has an opening 18 in the middle, through which the total exhaust gas stream flows after mixing in the direction of the honeycomb body. The guide surface 8 in the manner of an annular diaphragm is flush at its outer edge 19 with a casing tube of the honeycomb body, so that there is no flow through an exhaust gas stream. An alternative to this provides that evenly and / or unevenly distributed cutouts 20, which are indicated by dashed lines in Fig. 3, also allow a flow along the outer edge 19 and / or that the guide surface 8, as in the right

3, partially or completely evenly and / or unevenly distributed holes 29 through which exhaust gas can flow. In addition, a second such guide surface between the first guide surface and the honeycomb body can be arranged offset one behind the other and have different flow cross sections.

Fig. 4 shows a second embodiment of a guide surface 8. This has a first surface 21 and a second surface 22. The first and the second

Surfaces 21, 22 are curved and have an opening 18 in approximately their center Flow. The curvatures 23 support the deflection of the exhaust gas streams striking the surfaces 21, 22. Furthermore, both surfaces 21, 22 each have a border 24 which is irregularly and differently curved. This design supports the swirling of the exhaust gas flows among one another, which is not required by the fact that, for example, two such guide surfaces are staggered one behind the other. The guide surface (s) is / are designed in such a way that the resulting total exhaust gas flow is again distributed after flow through, if possible without a separation flow, over a total cross section of the end face of the subsequent honeycomb body to be flown.

5 shows a third exemplary embodiment of a guide surface 8. This has a third surface 25 and fourth surface 26. In addition to an approximately centrally arranged opening 18 there is also an outer edge 19 and the respective third surface 25 or fourth surface 26 Edge opening 27. This has the effect that behind the surfaces 25, 26 there is no dead flow region. Rather, the flow through the edge opening 27 leads to the formation of a negative pressure area along the sides of the surfaces 25, 26 facing the honeycomb body. This has the effect that the total exhaust gas flow when flowing through at least one or even two guide surfaces 8 according to FIG. 5 occurs again in a very short way distributed over the entire free flow cross section of the jacket tube.

Fig. 6 shows the guide surface 8 of FIG. 5 in cross section along the line VI-VI. A material ring 28 can be seen, to which the third surface 25 and fourth surface 26 are attached. Furthermore, the respective curvature 23 of both surfaces 25, 26 for deflecting and backflow of the incident exhaust gas flows can be seen.

It should also be pointed out that the guide surfaces 8 preferred according to the invention do not have to be annular as described. Partial segment-shaped guide surfaces can also be arranged, which do not have to be arranged with one another on the same level as an adjacent guide surface. Rather, as with the arrangement of a plurality of annular guide surfaces, these can be offset from one another and also each have a different design.

Reference list

Exhaust system

Collector

Jacket tube first flange, then second flange

Dividing plane

Honeycomb body first guide surface

Outlet cross-section to flow through first exhaust gas stream second exhaust gas stream third exhaust gas stream fourth exhaust gas stream

Whirl room

End face of the honeycomb body 7

Total exhaust gas flow

Opening outer edge

Cutout first surface second surface

Bulge

Boundary third surface fourth surface

Edge opening

Material ring hole

Distance between face and outlet cross-section

Claims

Patent claims

1. Exhaust system (1) with a collector (2) for merging exhaust gas flows (11, 12, 13, 14) from two or more cylinders one

Internal combustion engine, the collector (2) having an outlet cross-section (9), behind which a jacket tube (3) connects, in which a honeycomb body (7) is arranged, characterized in that between the outlet cross-section (15) and the honeycomb body (7 ) is a space (10) to be flowed through, in which at least one first guide surface

(8) for deflecting at least some of the exhaust gas flows (11, 12, 13, 14) is arranged.

2. Exhaust system (1) according to claim 1, characterized in that the first guide surface (8) is arranged so that a direct flow to the

Exhaust gas flows (11, 12, 13, 14) to the honeycomb body (7) is at least partially blocked.

3. Exhaust system (1) according to claim 1 or 2, characterized in that the first guide surface (8), which is designed in particular as a type of aperture, reduces the free cross section behind the outlet cross section (9), which is again the free cross section of the Jacket tube (3) connects.

4. Exhaust system (1) according to one of the preceding claims, characterized in that the first guide surface (8) evenly and / or non-uniformly, partially or entirely distributed holes (29) and / or cutouts (20) on the lateral outer edge (19) and / or at least one edge opening (27) and / or at least one curvature (23) on at least one of its surfaces (21, 22, 25, 26).

5. Exhaust system (1) according to one of the preceding claims, characterized in that a swirl chamber (15) is formed between the outlet cross section (9) and the first guide surface (8).

6. Exhaust system (1) according to one of the preceding claims, characterized in that the first guide surface (8) is arranged closer to the outlet cross-section (9) than to the honeycomb body (7).

7. Exhaust system (1) according to one of the preceding claims, characterized in that in the space to be flowed through (10) between the first guide surface (8) and the honeycomb body (7) a second guide surface is arranged.

8. collector (2) for an exhaust system (1), in particular according to one of claims 1 to 7, characterized in that at least a first

Guide surface (8) is part of the collector (2).

9. honeycomb body (7) in a casing pipe (3) for an exhaust system (1), in particular according to one of claims 1 to 7, characterized in that at least a first guide surface (8) is part of the casing pipe (3).

10. honeycomb body (7) according to claim 9, characterized in that the first guide surface (8) is in particular designed as a type of aperture and in the casing tube (3) with a distance (A) in front of the honeycomb body (7) is integrated.

11. A method for applying a honeycomb body (7) with exhaust gas flows (11, 12, 13, 14), which at least partially reach the honeycomb body (7) from different directions, characterized in that the exhaust gas flows (11, 12, 13, 14) before hitting the Honeycomb bodies (7) are deflected by at least one first guide surface (8) in such a way that they flow at least partially in a direction opposite to the exhaust gas flows (11, 12, 13, 14) and thus strike the honeycomb body (7) with a delay.

12. The method according to claim 11, characterized in that the exhaust gas flows (11, 12, 13, 14) flow pressure pulsating onto the honeycomb body (7) and a smoothing of the pressure pulses takes place by the deflection.

13. The method according to claim 11 or 12, characterized in that the exhaust gas flows (11, 12, 13, 14) flow to the honeycomb body (7) at different times.

14. The method according to any one of claims 11 to 13, characterized in that the exhaust gas flows deflected by the first guide surface (8) (11, 12,

13, 14) flow through a second guide surface.