EXHAUST SYSTEM FOR A VEHICLE

Abstract

An exhaust system, in particular for a vehicle with a diesel engine, has a first insert through which exhaust gas flows, a second insert through which exhaust gas flows and which is arranged downstream of the first insert in the flow direction, and an injection device arranged between the first and second inserts for injecting a fluid. A swirling element is provided in the flow path of the exhaust gas downstream of the first insert in the flow direction.

Description

RELATED APPLICATION

This application claims priority to German application 10 2008 053 669.5, which was filed Oct. 29, 2008.

BACKGROUND OF THE INVENTION

The present invention relates to an exhaust system, in particular for a vehicle with a diesel engine.

Such exhaust systems typically include a first insert through which exhaust gas flows, a second insert through which exhaust gas flows, and which is arranged downstream thereof in the flow direction, and an injection device arranged between the inserts for injecting a fluid. The inserts are filter units which are usually a block of ceramic material allowing through flow of exhaust gas. The insert can merely provide a filter function and/or have catalytic properties.

To comply with specifications as provided by environmental law, the amount of the particulate matter contained in the exhaust gas of a diesel engine needs to be reduced. To this end, particulate filters are built into the exhaust systems of vehicles for retaining the particles contained in the exhaust gas. To prevent an impairment of the function of the filter and, hence, of the exhaust system by the particles accumulating on the filter surface, the filter must be regenerated from time to time. This is effected by combusting the particles accumulated on the filter surface by the addition of heat.

To generate the temperatures necessary for the combustion, an oxidizable liquid, for example, is introduced into the exhaust gas flow upstream of the particulate filter, the liquid reacting with the residual oxygen contained in the exhaust gas. To achieve a uniform regeneration of the particulate filter, the combustion reaction must proceed distributed as uniformly as possible over the entire cross-section of the exhaust pipe.

It is the object of the present invention to provide an exhaust system which allows a uniform development of heat and thus a uniform combustion of the particles.

SUMMARY OF THE INVENTION

The present invention provides an exhaust system, in particular for a vehicle with a diesel engine, including a first insert through which exhaust gas flows, a second insert through which exhaust gas flows, and which is arranged downstream thereof in the flow direction, and an injection device arranged between the first and second inserts for injecting a fluid. A swirling element is provided in the flow path of the exhaust gas downstream of the first insert in the flow direction. In the swirl produced by the swirling element, the fluid introduced is mixed more homogeneously with the exhaust gas stream. This results in a more uniform distribution of the fluid over the entire flow cross-section, so that a better development of heat, and thus a more effective regeneration of the subsequent second insert are achieved.

In one example, the swirling element includes recesses through which the exhaust gas flows. This allows an effective control of the exhaust gas flow and, hence, a good deflection or a good swirling of the exhaust gas flow.

To influence the entire exhaust gas flow and to reach a complete mixing of the exhaust gas and the fluid, the swirling element ideally extends across the entire cross-section of the exhaust pipe.

A particularly uniform distribution of the fluid is attained in that the swirling element produces swirls over the entire cross-section of the exhaust pipe.

In one example, the swirling element includes deflector plates which are inclined in relation to the flow direction. They are arranged in the exhaust gas stream and deflect the exhaust gas stream or parts thereof, so that an eddy is produced downstream of the swirling element.

The angle at which these deflector plates are disposed with respect to the exhaust gas flow has great influence on the effectiveness of the swirling element. It is therefore of advantage for the deflector plates to include at least two portions which are inclined at different angles in relation to the flow direction.

It is especially advantageous if the angle of inclination of the portions increases in the flow direction. This allows the exhaust gas stream to be influenced very effectively.

Ideally, the deflector plates are inclined at an angle of at least 30° in relation to the flow direction.

The deflector elements may, for example, be arranged radially and distributed evenly over the entire cross-section.

The deflector elements are more particularly arranged similarly to a stator of a turbine and generate an eddy downstream of the swirling element in which the fluid introduced can be effectively distributed over the entire cross-section of the exhaust pipe.

The radially arranged deflector elements may, for example, enclose an opening in the middle of the swirling element, through which the exhaust gas stream can flow.

A baffle plate, disposed perpendicularly to the flow direction, may be provided in front of this opening. The baffle plate directs the exhaust gas stream onto the deflector elements.

The deflector elements may, however, also be arranged parallel to each other, so that as a whole they constitute a grid structure by which the exhaust gas stream is diverted.

To enhance the effect of the swirling element, the cross-sectional area of the exhaust pipe, through which exhaust gas flows, tapers in a portion located directly upstream of the swirling element in the flow direction, and/or widens in a portion located directly downstream of the swirling element in the flow direction. A tapering of the cross-sectional area upstream of the swirling element causes an increase in the approach velocity, so that the exhaust gas stream impinges on the swirling element at a higher velocity. In addition, the reduced cross-section results in a more favorable ratio of the pipe cross-section to the vaporizer. The widening of the cross-sectional area downstream of the swirling element, on the other hand, causes the exhaust gas stream to be decelerated, so that the fluid is allowed to mix with the exhaust gas stream over a longer period of time.

The inserts may be particulate filters, for example, more particularly diesel particulate filters. Owing to the swirling element, a fluid introduced can combust homogeneously, so that a uniform regeneration of the entire filter surface is achieved.

The first insert is, e.g., a pre-filter and the second insert may be a diesel particulate filter with a diesel oxidation catalytic converter. Because of such a diesel oxidation catalytic converter, the exhaust gas temperature may be further increased, so that the subsequent filter may be regenerated more effectively. The swirling element arranged upstream swirls the exhaust gas stream with the fluid contained therein, so that the entire surface area of the diesel oxidation catalytic converter can be used.

Preferably, the injection device is part of a regeneration device. By using such a regeneration device, an oxidizable liquid is introduced into the exhaust gas stream which, based on an exothermic reaction with the oxygen of the exhaust gas, leads to an increase in temperature by which a particulate filter arranged downstream can be regenerated.

For this purpose, the injection device includes a fuel vaporizer, which vaporizes the fuel before it is injected into the exhaust pipe, so that the fuel mixes well with the exhaust gas stream and reacts more readily with the residual oxygen in the exhaust gas.

Such an injection device may be arranged upstream or downstream of the swirling element. In this way, the fluid is either introduced into the exhaust gas stream prior to the swirling and is mixed with the exhaust gas stream by the swirling element, or the fluid is introduced downstream of the swirling element into the eddy already generated.

The injection device may also be integrated in the swirling element, for example, for reasons of space.

In one example, the first insert and the second insert along with the swirling element are arranged in a shared housing. This results in a very compact design of the exhaust system.

The swirling element may be a static mixer, i.e. the swirling element does not have any moving parts, and no external control of, for example, the deflector plates is required.

The swirling element is a prefabricated component that is inserted in the exhaust pipe.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective partial sectional view of an exhaust system according to the invention;

FIG. 2 shows a perspective sectional view in a longitudinal section taken through the exhaust system of FIG. 1;

FIG. 3 shows a further sectional view of the exhaust system of FIG. 1;

FIG. 4 shows a partial sectional view of a further embodiment of an exhaust system according to the invention;

FIG. 5 shows a third embodiment of an exhaust system according to the invention;

FIG. 6 shows a fourth embodiment of an exhaust system according to the invention;

FIG. 7 shows a swirling element for the exhaust system from FIG. 1;

FIG. 8 shows a second embodiment of a swirling element;

FIG. 9 shows a third embodiment of a swirling element;

FIG. 10 shows a fourth embodiment of a swirling element;

FIG. 11 shows a sectional view of an exhaust system according to the invention with the swirling element from FIG. 10; and

FIG. 12 shows a fifth embodiment of a swirling element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The exhaust system 10 shown in FIG. 1 of a diesel vehicle has a housing 12 including a first housing part 14 and a second housing part 16, which are connected by a flange 18, 20. As shown in FIG. 2, the first housing part 14 surrounds a first insert 22, here a pre-filter; the second housing part 16 surrounds a second insert 24, which in this case is a diesel particulate filter with a diesel oxidation catalytic converter. The first and second inserts 22, 24 are mounted in the housing 12 at a distance from each other, so that a cavity 26 FIG. 3) is provided between them. Provided on the housing 12 between the first insert 22 and the second insert 24 is an injection device 28 through which a liquid or vapor may be introduced into the cavity 26. The exhaust gas flows through the exhaust system 10 in the flow direction A and is pre-filtered by the first insert 22 before the exhaust gas flows through the second insert 24.

The fluid introduced into the cavity 26 is an oxidizable liquid, in this case a fuel, which combusts with the residual oxygen present in the exhaust gas of a diesel engine in an exothermic reaction at the oxidation catalytic converter. Owing to the heat produced in the process, a particulate filter disposed downstream in the flow direction A can be regenerated, i.e. the residual particles accumulated in this particulate filter are combusted in a controlled manner by the heat generated. This process is assisted by the diesel oxidation filter arranged downstream of the injection device 28, since the exhaust gas temperature is further increased by this filter.

A swirling element 30 is arranged in the exhaust gas stream between the injection device 28 and the second insert 24. The swirling element extends across an entire cross-section of the exhaust system 10. As can be seen in FIG. 2, the swirling element 30 has a circular central opening 32 and a deflector element 34 that is arranged in the middle of the circular central opening 32.

The exhaust gas stream enriched with the fluid flows through the circular central opening 32 and is swirled downstream thereof. This results in an improved mixing of the exhaust gas stream with the fluid, so that the fluid impinges in an evenly distributed state on the second insert 24 located downstream thereof in the flow direction A.

FIGS. 4 to 6 show further embodiments of an exhaust system 10 according to the invention. The exhaust systems 10 have essentially the same components as the exhaust system 10 from FIG. 1, so that the same reference numbers are used for like components.

The exhaust system 10 in FIGS. 4 to 6 includes an additional intermediate portion 36 downstream of the swirling element 30 in the flow direction. This intermediate portion provides an additional cavity 38 downstream of the swirling element 30, in which the fluid can be better mixed with the fuel.

Compared with the first and second housing parts 14 and 16, the intermediate portion 36 of the exhaust system 10 shown in FIG. 5 has a markedly reduced cross-section. The cross-section of the exhaust pipe is reduced immediately downstream of the swirling element 30 in the flow direction A and is widened again immediately upstream of the second insert 34. This leads to an increase occurring in the flow velocity of the exhaust gas stream downstream of the swirling element 30, as a result of which a better swirling can be achieved.

In addition to the intermediate portion 36 arranged downstream of the swirling element 30, the exhaust system 10 shown in FIG. 6 has a second intermediate portion 40 disposed upstream of the swirling element 30, which is conically tapered and opens directly into the swirling element 30. The swirling element 30 has a substantially smaller cross-sectional flow area than that of the first and second inserts 22, 24. The intermediate portion 36 downstream of the swirling element 30 is conically widened. Owing to the reduction in the cross-section through which exhaust gas flows, an increase in the flow velocity occurs upstream of and in the swirling element 30. The exhaust gas stream impinges upon the swirling element at a higher velocity. Upstream of the swirling element 30, the cross-section of the exhaust system 10 conically widens in a portion 40, so that a deceleration of the flow velocity is brought about here.

In each of the embodiments shown, the injection device 28 is arranged upstream of the swirling element 30, so that the liquid or the vapor is introduced into the exhaust gas stream prior to the swirling.

However, the injection device 28 could also be arranged downstream of the swirling element 30.

Embodiments in which the injection device 28 is integrated in the swirling element 30 are also conceivable.

The injection device 28 is part of a regeneration device and includes a fuel vaporizer by which fuel is introduced into the exhaust system 10 in a vaporous condition. But other oxidizable liquids may also be introduced into the exhaust system 10. In particular, the liquid need not be vaporized before it is introduced into the exhaust pipe.

FIGS. 7 to 12 each show detail views of a swirling element 30 as inserted. The swirling elements 30 each extend across the entire cross-section of the exhaust pipe and include at least one opening 32 through which the exhaust gas stream can flow. But it is also possible for the swirling element 30 to extend only across part of the cross-section. In particular, the swirling element 30 need not have an opening 32, but may guide the exhaust gas stream past the swirling element 30, for example.

The swirling element 30 in FIGS. 7 to 10 each includes a plurality of radially arranged, uniformly distributed deflector elements 34 in the shape of guide blades. The deflector elements 34 in FIGS. 7 to 9 each have a plurality of portions 42, 44, which are inclined at different angles in relation to the flow direction A. The second portion 44 of the deflector element 34 is arranged downstream of the first portion 42 in the flow direction A here and has a greater angle in relation to the exhaust gas flow.

The number of the deflector elements 34 and the shape and arrangement thereof in the swirling element 30 may be varied as desired. In particular, the number of the portions 42, 44 of a deflector element, as well as the angle thereof in relation to the exhaust gas stream, may be altered as desired. The slope of a deflector element 34 may also be altered continuously, for example, similar to a turbine blade.

A baffle plate 46 is provided in the middle of each swirling element 30. The baffle plate 46 is disposed perpendicularly to the exhaust gas flow. This baffle plate 46 causes the exhaust gas stream to be directed more effectively onto the deflector elements 34. However, embodiments without a baffle plate 46 are also conceivable.

Such an embodiment is shown, for example, in FIG. 10 and FIG. 11. The swirling element 30 shown here likewise includes a plurality of radially arranged, blade-type deflector elements 34. The angle of the deflector element 34 continuously increases as the flow proceeds.

In addition, the outer casing of the swirling element 30 is designed to be conically tapered in the region of the deflector elements 34. This results in a simultaneous increase in the flow velocity while the exhaust gas stream is deflected by the deflector elements 34.

In a region downstream of the deflector elements 34, the outer casing of the swirling element 30 is conically widened here, so that a deceleration of the flow velocity is brought about again. As can be seen in FIG. 11, in this embodiment the injection device 28 is arranged downstream of the swirling element 30 which constitutes a portion of the exhaust pipe.

A further embodiment of a swirling element 30 is apparent from FIG. 12. The deflector elements 34 here are arranged parallel to each other at the same angle relative to the exhaust gas stream and form a grid together with metal reinforcement sheets 48. While in this case the deflector elements 34 all have the same angle in relation to the exhaust gas stream, it is also conceivable that the deflector elements 34 are arranged at different angles or include a plurality of portions 42, 44 of different inclinations.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. An exhaust system, in particular for a vehicle with a diesel engine, comprising:

a first insert through which exhaust gas flows;

a second insert through which exhaust gas flows and which is arranged downstream of the first insert in a flow direction;

an injection device arranged between the first and the second inserts for injecting a fluid; and

a swirling element arranged downstream of the first insert in a flow path of the exhaust gas.

2. The exhaust system according to claim 1, wherein the swirling element includes recesses through which the exhaust gas flows.

3. The exhaust system according to claim 1, wherein the swirling element extends across an entire cross-section of an exhaust pipe.

4. The exhaust system according to claim 1, wherein the swirling element produces swirls over an entire cross-section of an exhaust pipe.

5. The exhaust system according to claim 1, wherein the swirling element includes deflector elements which are inclined in relation to the flow direction.

6. The exhaust system according to claim 5, wherein the deflector elements include at least two portions which are inclined at different angles of inclination in relation to the flow direction.

7. The exhaust system according to claim 6, wherein the angle of inclination of the portions increases in the flow direction.

8. The exhaust system according to claim 5, wherein the deflector elements are inclined at an angle of at least 30° in relation to the flow direction.

9. The exhaust system according to claim 5, wherein the deflector elements extend in a radial direction and are evenly distributed over an entire cross-section of an exhaust pipe.

10. The exhaust system according to claim 9, wherein the deflector elements are configured in the shape of turbine blades.

11. The exhaust system according to claim 9, wherein radially arranged deflector elements enclose an opening.

12. The exhaust system according to claim 11, including a baffle plate disposed perpendicularly to the flow direction and in front of the opening.

13. The exhaust system according to claim 5, wherein the deflector elements are arranged parallel to each other.

14. The exhaust system according to claim 1, wherein a cross-sectional area of an exhaust pipe through which exhaust gas flows, tapers in a portion located directly upstream of the swirling element in the flow direction and/or widens in a portion located directly downstream of the swirling element in the flow direction.

15. The exhaust system according to claim 1, wherein the first and second inserts are particulate filters and/or catalytic converters.

16. The exhaust system according to claim 1, wherein the first insert is a pre-filter and the second insert includes a diesel oxidation catalytic converter and/or particulate filter.

17. The exhaust system according to claim 1, wherein the injection device is part of a regeneration device.

18. The exhaust system according to claim 17, wherein the injection device includes a fuel vaporizer.

19. The exhaust system according to claim 1, wherein the injection device is arranged upstream or downstream of the swirling element.

20. The exhaust system according to claim 1, wherein the injection device is integrated in the swirling element.

21. The exhaust system according to claim 1, wherein the first insert and the second insert along with the swirling element are arranged in a shared housing.

22. The exhaust system according to claim 1, wherein the swirling element is a static mixer.

23. The exhaust system according to claim 1, wherein the swirling element is a prefabricated component that is inserted in an exhaust pipe.