WO2013000640A1 - Device and method for introducing a reducing agent into an exhaust train - Google Patents

Abstract

The invention relates to a device for introducing a reducing agent into an exhaust train of an internal combustion engine having at least one hollow element (4, 6; 18) which is arranged in the exhaust train, and at least one feed line which is designed to feed reducing agent to the hollow element (4, 6; 18). The at least one hollow element (4, 6; 18) extends in a plane which is oriented transversely with respect to the direction of flow of the exhaust gases in the exhaust train. At least one opening (12) is formed in the hollow element (4, 6; 18), which opening (12) makes it possible for the reducing agent to be introduced into the exhaust train from the hollow element (4, 6; 18).

Description

 Description title

 Apparatus and method for introducing a reducing agent in an exhaust line

The invention relates to a device and a method for introducing a reducing agent into an exhaust line of an internal combustion engine in order to achieve the most uniform possible distribution of the reducing agent in the exhaust system.

State of the art:

In the development of internal combustion engines, the adherence to limit values for the pollutant emissions is the highest goal. In the case of diesel engines in particular, NOx reduction is absolutely necessary in order to comply with the prescribed limits.

One way of reducing NOx is Selective Catalytic Reduction (SCR). In this system, a urea water solution is sprayed into the exhaust tract. In the hot exhaust gases, ammonia gas develops, with which the nitrogen oxides can be selectively reduced.

The urea water solution can be added to the exhaust in various ways. Alternatively, the exhaust gases instead of a urea water solution and ammonia can be supplied in gaseous form.

DE 197 38 859 A1 shows a mixture delivery device for an exhaust system, in which an annular spray body, which has a circumferential distribution channel and a plurality of spray channels, is introduced into the exhaust gas line. Via a mixture supply line, a mixture of compressed gas and urea-water solution is fed and introduced into the exhaust gas flow upstream of the catalyst. Disclosure of the invention:

An object of the invention is to provide a device for injecting a reducing agent, in particular a gaseous reducing agent such as ammonia, into the exhaust gas line of an internal combustion engine with which the most uniform possible distribution of the reducing agent in the exhaust gas system is achieved.

The object is achieved by a device according to the invention according to independent claim 1 and a method according to claim 10. The dependent claims 2 to 9 describe advantageous embodiments of a device according to the invention.

An apparatus according to the invention for introducing a reducing agent into an exhaust gas line of an internal combustion engine has at least one hollow element arranged in the exhaust gas line and at least one feed line, which is designed to supply reducing agent to the hollow element. The at least one hollow element extends in a plane which is aligned transversely to the flow direction of the exhaust gases in the exhaust system. In the hollow element, at least one opening is formed which allows reducing agent to flow from the hollow element into the exhaust gas line.

The inventive arrangement of the hollow elements and openings of a device according to the invention, a uniform distribution of the concentration of the reducing agent in the exhaust line is achieved when introducing the gaseous reducing agent in the exhaust system. This results in an increase in efficiency, especially in the case of short mixing sections. In the case of direct metering of ammonia, a catalyst arranged in the exhaust gas line does not have to be thermo-thermally insulated. Hydrolysis perform, which is particularly advantageous at low temperatures.

The invention also includes a method of introducing a particular gaseous reducing agent into an exhaust line of an internal combustion engine, wherein the method includes in particular, the particular gaseous reducing agent through a device according to the invention in the exhaust system contribute. The inventive introduction of a particular gaseous reducing agent is a particularly homogeneous mixing of the introduced reducing agent with the exhaust gases, which flow through the exhaust line achieved. This allows a particularly effective reduction of the nitrogen oxides contained in the exhaust gases over the entire cross section of the exhaust system.

In one embodiment, the device according to the invention has at least one opening, which is oriented so that the reducing agent is parallel to the flow direction of the exhaust gases in the exhaust line from the hollow element in the

Exhaust line can flow. Alternatively or additionally, at least one of the openings may be aligned such that the reducing agent flows with a transverse component, in particular at a right angle, to the flow direction of the exhaust gases in the exhaust gas line into the exhaust gas line. Due to the orientation of the openings, through which the reducing agent emerges from the hollow element and in the

Exhaust line flows, the inflow angle, in which the reducing agent flows from the hollow element into the exhaust line, can be suitably adjusted to achieve an optimal and particularly particularly uniform distribution of the reducing agent in the exhaust gases in the exhaust system.

In one embodiment, the at least one hollow element is helical, so that it extends in a spiral shape from the center of the exhaust gas line into its edge region. In this case, the hollow element is preferably arranged in a plane which is aligned transversely, in particular perpendicularly, to the flow direction of the exhaust gases in the exhaust gas line. By a helical or spiral-shaped hollow element, the entire cross section of the exhaust gas line can be covered by a single hollow element. With a single hollow element, a uniform distribution of the reducing agent in the exhaust system can be achieved. The cost of additional hollow elements and their assembly can be saved.

The reducing agent can be supplied to the hollow element in the center of the exhaust gas line, so that it flows through the helical element into the outer regions of the exhaust gas line. Alternatively, the reducing agent can be supplied to the screw or spiral hollow element at its outer end, so that it flows through the hollow element in the direction of the center of the exhaust gas line. Along the course of the hollow element, openings are formed through which, during operation, in each case a part of the reductant Onsmittels flows from the hollow element in the exhaust line and the reducing agent is distributed uniformly over the entire cross section of the exhaust line. In one exemplary embodiment, the at least one hollow element extends in the radial direction through the cross section of the exhaust gas line. Along the course of the hollow element, openings are formed through which a part of the reducing agent in each case flows out of the hollow element into the exhaust gas line during operation. By means of a hollow element extending in the radial direction through a cross section of the exhaust gas line, different regions at different radial distances from the center or the periphery of the exhaust gas line can be uniformly supplied with reducing agent.

In one embodiment, a plurality of hollow elements are provided, and the hollow elements are preferably arranged in the form of a grid, which is aligned transversely, in particular at a right angle to the flow direction of the exhaust gases in the exhaust system. In each of the hollow elements, a number of openings is provided, which allow an exit of reducing agent in the exhaust system.

By lattice-shaped arranged hollow elements, in each of which a plurality of openings are formed, the cross section of the exhaust line can be particularly evenly supplied with reducing agent, so that a particularly homogeneous mixing of the exhaust gases in the exhaust line with the supplied reducing agent can be achieved.

In one embodiment, mixer flaps are arranged on and / or between the hollow elements, which flaps are designed to deflect or deflect the exhaust gas flow in the exhaust gas line. By such mixer flaps, which deflect the exhaust gas flow in the exhaust line or divert the mixing of the exhaust gases can be improved with the reducing agent in order to achieve the most homogeneous distribution of the reducing agent in the exhaust gases.

In one embodiment, an annular feed line is provided, which is designed to supply the hollow element or the hollow elements with the reducing agent to be introduced into the exhaust gas line. An annular feed line may be formed inside or outside the exhaust line. Through an annular feed line, the reducing agent is particularly uniform in the exhaust gas sträng arranged hollow elements fed, whereby a particularly homogeneous distribution of the reducing agent is achieved in the exhaust system.

In one embodiment, the device according to the invention for introducing the reducing agent is attached to a sealing ring or flange, which is arranged in the exhaust pipe. At a arranged in the exhaust gas ring and / or flange, a device according to the invention can be mounted particularly simple and inexpensive. In particular, additional interruptions (cuts) in the exhaust pipe, which can lead to leakage, can be avoided.

The invention will be explained in more detail below with reference to the attached figures. Showing:

Figure 1 shows a first embodiment of a device according to the invention.

Figure 2 shows a second embodiment of a device according to the invention.

Figure 3 shows a third embodiment of a device according to the invention.

Figure 4 shows a fourth embodiment of a device according to the invention.

Figure 5 shows a fifth embodiment of a device according to the invention.

6 shows a sixth embodiment of a device according to the invention.

In FIGS. 1 to 6, the exhaust gas line respectively extends perpendicular to the drawing plane, so that the figures show a cross section through the exhaust gas line.

In all figures, like reference numerals designate the same or similar components. A description of the components is provided only for the first embodiment, it being understood that the same description applies to the following embodiments, unless expressly stated otherwise. An inventive device according to a first embodiment, as shown in Figure 1, is disposed at a position of the exhaust line, at the two pipes of the exhaust line abut each other and the transition is sealed by a sealing ring 2.

The inventive device of the first embodiment has a ring line 8, which extends at the height of the sealing ring 2 around the circumference of the exhaust line and is connected at at least one point with a supply line 10. The supply line 10 is designed to supply the ring line 8 with the reducing agent to be injected, in this case a gaseous reducing agent, from an external source, not shown in FIG. 1.

Mutually opposite points of the ring line 8 are connected by hollow webs 4, 6, which enter through openings formed in the seal 2 in the exhaust line and extend through this.

The embodiment shown in Figure 1 has vertically extending webs 4 and horizontally extending webs 6, which form a rectangular grid in the interior of the exhaust system. However, the rectangular arrangement of the webs 4, 6 is only an example and also arrangements are conceivable in which the webs 4, 6 are arranged at a different angle to each other and so form a pointed or obtuse-angled grid.

On the webs 4, 6 mixer flaps 14 are attached, which are designed to divert the flowing perpendicular to the plane through the exhaust gas exhaust gases and in particular to swirl, so as homogeneous as possible

To cause mixing of the exhaust gases in the exhaust system with the injected reducing agent.

In the exemplary embodiment shown in FIG. 1, the mixer flaps 14 are designed such that they divert the exhaust gases flowing through the exhaust gas line alternately upwards and downwards; This achieves a particularly effective mixing of the exhaust gases with the injected reducing agent. The hollow webs 4, 6 are in communication with the ring line 8 and have openings 12 in the interior of the exhaust gas line. Reductant fed through the feed line 10 of the ring line 8 flows from the ring line 8 into the cavities formed in the webs 4, 6 and from there through the openings. 12 in the exhaust line, where it mixes with the swirled by the mixer flaps 14 exhaust gases to reduce by means of a downstream of the device arranged, not shown in the figure 1 catalyst, the nitrogen oxides contained in the exhaust gases.

FIG. 2 shows an alternative embodiment of a device according to the invention. Instead of webs 4, 6, which are arranged in the form of a rectangular grid, the hollow elements 18 are formed as three concentrically arranged around the center of the exhaust line rings which are connected by a radially extending from the outer periphery to the center of the exhaust line feed line 10 are. The supply line 10 leads the reducing agent from an external, not shown, source to the ring-shaped hollow elements 18. The annular hollow elements each have a number of openings 12, through which the reducing agent flows from the annular hollow elements 18 into the exhaust gas line. Between the annular hollow elements 18 mixer blades 14 are arranged to deflect the exhaust gases flowing through the exhaust line, and in particular to swirl to effect a uniform distribution of the supplied reducing agent with the exhaust gases. In the radial direction extending webs 20, which the annular hollow elements

18 connect together, increase the strength and in particular the rigidity of a device according to the invention according to the second embodiment. Figure 3 shows a third embodiment of a device according to the invention, which is arranged at the height of a flange 3, which is formed on an exhaust line. The flange 3 has in its outer region a number of holes 5, through which the flange 3 can be screwed to a second flange.

On the inner side of the flange 3 in the radial direction, a ring line 8 extending around the exhaust gas line is formed, which can be supplied with the reducing agent to be injected via a radial inlet 10. From the ring line 8 branch off a plurality of radial hollow elements 18, which extend from the periphery in the direction of the center of the exhaust line. The hollow elements 18 can all have the same length or, as shown in FIG. 3, different lengths and are each provided with a plurality of openings 12 formed, through which the reducing agent to be injected, which has been supplied to the radial hollow elements 18 through the inlet 10 and the ring line 8, can flow from the hollow elements 18 into the exhaust gas line. Figure 4 shows another embodiment of a device according to the invention, in which the hollow elements 18 are arranged comb-like. In the example shown in FIG. 4, the hollow elements 18 extend from the supply line 10 essentially parallel to one another through the exhaust gas line. It is understood that the hollow elements 18 can also be at a certain angle to each other.

The outgoing from the supply line 10, comb-like arranged hollow elements 18 may be fixed by webs, not shown in the figure 4 at the periphery of the exhaust line to increase the mechanical stability of the device.

Also in this embodiment, the hollow elements 18 each have a plurality of openings 12, passes through the injected reducing agent in operation from the hollow elements 18 in the exhaust line. These openings 12 may also be aligned parallel, obliquely and / or at a right angle to the flow direction of the exhaust gases in the exhaust gas line.

FIG. 5 shows a fifth exemplary embodiment of a device according to the invention. The device according to the fifth embodiment comprises a single hollow member 18 which extends in a spiral or helical shape from an outer region of the exhaust line to its center. Via a feed line 10 formed at an outer end of the hollow element 18, the hollow element 18 is supplied with the reducing agent to be injected. The reducing agent flows through the spiral element 18 from an outer peripheral portion of the exhaust line toward the center thereof. By openings 12 formed along the hollow element 18, a portion of the supplied reducing agent enters the exhaust gas line so that the reducing agent is introduced uniformly over the entire cross section into the exhaust gas line in order to achieve the most homogeneous possible mixing of the reducing agent with the exhaust gases in the exhaust gas line.

In the radial direction, adjacent regions of the helical hollow element 18 are connected to one another by webs 20 extending essentially in the radial direction in order to ensure the mechanical stability of the helical or spiral elements. Ralförmigen hollow element 18 to increase. In particular, such a hollow element 18, which is reinforced by radially extending webs 20, resistant to forces exerted by the exhaust gas flow in the exhaust line to the hollow member 18.

The screw or spiral hollow element 18 shown in FIG. 5 has approximately three turns. However, this is only an example and the number of turns can be suitably selected depending on the diameter of the exhaust line and the diameter of the hollow element 18.

FIG. 6 shows a further exemplary embodiment of a device according to the invention, which likewise has a helical element or spiral-shaped hollow element 18 which extends in a plane of the exhaust gas line which is oriented at right angles to the flow direction of the exhaust gases in the exhaust gas line.

In contrast to the exemplary embodiment shown in FIG. 5, the feed line 10, through which the reducing element to be introduced is fed, extends radially from the outer region of the exhaust gas line to its center, where it merges into the hollow element 18, so that the fuel injected Reducing agent is supplied to the hollow member 18 through the supply line 10 in the center of the exhaust line, and flows through the hollow member 18 spirally to the outside. In each case, a portion of the reducing agent passes through formed in the hollow member 18 openings 12 in the exhaust line.

In this exemplary embodiment too, regions of the hollow element 18 which are adjacent to one another in the radial direction are connected to one another by webs 20 running in the radial direction in order to increase the mechanical stability of the device and in particular of the hollow element 18.

5 and 6 may additionally be arranged on the webs 20, as shown in FIGS. 1 and 2, in order to influence the exhaust gas flow in the exhaust gas line and to achieve better mixing of the exhaust gases with the injected reducing agent.

In all exemplary embodiments shown, the openings 12 can be arranged both parallel to the flow direction of the exhaust gases in the exhaust gas system and at any desired, in particular right angle to the flow direction of the exhaust gases. be net in order to achieve an optimal, in particular homogeneous mixing of the injected reducing agent with the exhaust gases flowing through the exhaust line.

The openings 12 preferably have a diameter which is in each case smaller than one tenth of the diameter of the respective hollow element 4, 6, 18 in order to keep the pressure drop in the hollow element 4, 6, 18 as low as possible over its course and thus a uniform introduction of the reducing agent to ensure in the exhaust system.

A device according to the invention, as shown by way of example in FIGS. 1 to 6, makes it possible to effectively introduce a gaseous reducing agent into the exhaust gas line of an internal combustion engine, thereby achieving a very even distribution of the reducing agent in the exhaust gas line. The invention is not limited to the embodiments shown in the figures, but includes all embodiments that fall within the scope of the following claims.

Claims

claims 1 . Device for introducing a reducing agent in an exhaust line of an internal combustion engine, with  at least one hollow element (4, 6; 18) arranged in the exhaust gas line, wherein in the hollow element (4, 6; 18) at least one opening (12) is formed, which makes it possible to remove the reducing agent from the hollow element (4, 6; ) to introduce into the exhaust gas line, and  at least one feed line, which is designed to supply the reducing element to the hollow element (4, 6, 18),  characterized,  in that the at least one hollow element (4, 6, 18) extends in a plane which is aligned transversely to the flow direction of the exhaust gases in the exhaust gas line. 2. Device according to claim 1, wherein the at least one opening (12) is aligned so that the reducing agent flows parallel to the flow direction of the exhaust gases from the cavity (4, 6, 18) in the exhaust line. 3. Device according to claim 1, wherein at least one opening (12) is aligned so that the reducing agent flows with a transverse component to the flow direction of the exhaust gases in the exhaust line, in particular at right angles, from the cavity (4, 6, 18) in the exhaust line. 4. Device according to one of the preceding claims, characterized in that the at least one hollow element (18) is helical. 5. Device according to one of the preceding claims, characterized in that the at least one hollow element (18) extends in the radial direction through the exhaust gas line. 6. Device according to one of the preceding claims, characterized in that a plurality of hollow elements (4, 6) are provided and the hollow element are arranged (4, 6) in the form of a grid transversely to the flow direction of the exhaust gases in the exhaust line. 7. Device according to one of the preceding claims with an annular feed line (8) which is arranged along the circumference of the exhaust line and formed to supply the at least one hollow element (4, 6, 18), the reducing agent. 8. Device according to one of the preceding claims, wherein the device has mixer flaps (14) which are designed to influence the exhaust gas flow in the exhaust line and in particular to deflect. 9. Device according to one of the preceding claims, wherein the device is arranged on a flange (3) or a sealing ring (2) of the exhaust line. 10. A method of introducing a reducing agent, in particular a gaseous reducing agent, in an exhaust line of an internal combustion engine, wherein the method includes, to introduce the gaseous reducing agent by a device according to one of claims 1 to 9 in the exhaust line.