WO2012052560A1 - Fitting for introducing reductant - Google Patents

Abstract

The invention relates to a fitting (2) to be arranged at an opening (12) of an exhaust gas line (1), of an exhaust gas system, that conducts an exhaust gas flow and for injecting a reductant. The reductant is injected into the exhaust gas line (1) by means of an injection nozzle (3) installed on the fitting (2). The fitting (2) forms a channel (21), which surrounds the center axis (20) of the fitting and conducts reductant into the exhaust gas line (1) and is closed from the injection nozzle (3) to the exhaust gas line (1). The aim of the invention is to improve the distribution of the reductant. For this purpose, the fitting (2) has a flange collar (23), which at least partially surrounds the channel (21), and protrudes with the channel (21) into the exhaust gas line (1).

Description

 Nozzle for introducing reducing agent

The invention relates to a nozzle for arranging at an opening of an exhaust gas flow leading exhaust pipe having a central axis and for flanging an injection nozzle for a reducing agent. The nozzle forms a circumferential around its central axis, the reducing agent in the exhaust pipe leading channel, which projects into the exhaust pipe. Furthermore, the nozzle has an at least partially circumferential flange collar around the channel.

It is already a generic nozzle for a metering device known from DE 198 20 990 AI, in which a nozzle is partially guided in an exhaust pipe, wherein the nozzle is arranged at right angles to the flow direction. The nozzle far a through holes formed as, arranged parallel to the flow direction through hole.

In EP 1 748 162 AI perforated plates are described, which are introduced into the exhaust pipe and cause the atomization of the reducing agent.

The invention has the object of providing a nozzle in such a way and to arrange that is easy to assemble and at the same time the injected into the exhaust pipe reducing agent spreads as quickly and uniformly over the entire cross section of an exhaust pipe under the influence of the flow of the exhaust gas.

The object is achieved according to the invention in that the flange collar to one, to the central axis of the exhaust pipe coaxial to be arranged axis, is curved parallel to the peripheral surface of the exhaust pipe and the nozzle with the flange collar middle or directly on the exhaust pipe can be placed. The radius of curvature of the nozzle corresponds to the pipe radius of the exhaust pipe.

This ensures that the nozzle in any orientation to the exhaust pipe can be easily placed on the exhaust pipe and welded tight to the flange collar. A

It may also be advantageous for this purpose if an angle ms between 25 ° and 65 ° is formed between the central axis and the axis. A flat orientation of the channel with respect to the exhaust gas line causes the reducing agent to be deflected less strongly from the direction of injection into the flow direction, and thus the flow-related influences on the side of the reducing agent are reduced to the preferred distribution in the exhaust line. At the same time a distribution of the reducing agent over a large part of the cross section of the exhaust pipe is already achieved centrally in the channel by the relatively wide to the diameter of the exhaust pipe outlet region of the channel. By this measure, the required mixing distance for the distribution of the reducing agent in the flow direction over other injection z-geometries can be shortened.

Accordingly, it is advantageous that the channel in the radial direction to the axis by at least 30% of a diameter Da of the exhaust pipe protrudes into the exhaust pipe. As a result, the reducing agent is introduced to the middle of the exhaust pipe to the central flow axis. Further, it may be advantageous if the projecting into the exhaust pipe channel has a channel wall portion having a length Lmax in the direction of a channel wall, which corresponds to at least 80% of a maximum diameter Dmax of the opening. Fluidically, a long channel is advantageous because the exhaust gas flow can form along the channel and there is the possibility of heating the channel more strongly by the exhaust gas. By not all of the reducing agent enters the exhaust pipe in the edge region of the exhaust pipe and is detected by the exhaust gas flow and carried in the flow direction, but a large part of the reducing agent only further inside the exhaust pipe before and behind the central flow axis. Although the reducing agent is already partially detected in the edge region of the exhaust pipe from the exhaust stream, but in a reduced compared to the relevant prior art, because the exhaust stream is first deflected in the flow direction through the channel and thus not directly the reductant, but detected in the flow shadow of the channel , For this, the channel can form a closed lateral surface.

It is advantageous if the channel wall portion is arranged with the length Lmax in the radial direction to the central flow axis below the opening. As a result, deposits of the reducing agent are prevented on the side opposite the neck of the exhaust pipe. The channel wall section forms a kind of collecting tray for the reducing agent.

It may advantageously be provided that the projecting into the exhaust pipe channel has regularly or irregularly distributed holes, which can be detected by a detectable in the channel pattern of special flow vectors the flow are arranged. Flows are generated through the holes on the inner surface of the channel in the direction of the exhaust pipe, where without such holes flows prevail in the direction of the injection nozzle, which can be mapped with flow vectors. In addition, a portion of the exhaust gas is passed through the holes in the channel and the channel heated inside. The increased temperature in the channel also reduces the crystallization of the reducing agent.

Of particular importance may be for the present invention, when the holes are aligned in the radial direction to the central axis or at an angle b to the radial direction employed. The orientation of the holes depends primarily on which flows acting on the inner surface in the direction of the injection nozzle must be counteracted. Depending on the orientation of the flow vector, the respective hole is more or less employed.

For this orientation is particularly advantageous that at least the channel is designed as a casting with a wall thickness between 2.4 mm and 5.3 mm, the holes depending on the alignment nozzles with a length LI between 2.4 mm and 6.8 mm form. Due to the strength of the channel wall, the holes are correspondingly long and thus form a kind of nozzle for the flow. For holes that are arranged at right angles to the channel wall, the length LI corresponds to the wall thickness. However, when the holes are set against the duct wall, the length LI increases and the jet effect is enhanced.

In connection with the construction and arrangement according to the invention, it may be advantageous if the gas pipe projecting channel between 6 and 50 holes. The channel serves as a guide for the reducing agent, so that it must be avoided to make a kind of perforated plate through too many holes from the channel, in which the sum of the cross sections of the holes would correspond approximately to the remaining channel surface.

It can also be advantageous if the channel is free of holes in the region of the channel wall section below the central axis. This also deposits of the reducing agent are avoided on the opposite side of the channel of the exhaust pipe.

In addition, it may be advantageous if, in the flow direction of the exhaust gas after one or more holes, a spoiler is arranged on the channel, with which a part of the exhaust gas flow can be diverted from a central flow axis and directed into the respective hole. The through the holes of the upper part of the channel is actively flushed by the fact that the flow is diverted within the exhaust pipe branched off from the exhaust pipe in the upper region of the channel in which the injection direction is arranged.

It may be advantageous if the spoiler is concave against the flow direction and at least two holes are arranged in the flow direction in front of the spoiler. Due to the concave design of the back pressure in the flow direction is increased in front of the spoiler and reinforced the rinsing effect.

Furthermore, it can be advantageous if a cross-sectional area Qk of the channel at the end of the connecting piece in the exhaust pipe corresponds to between 30% and 80% of a pipe cross-sectional area Qa of the exhaust pipe. The pipe cross-sectional area Qa of the exhaust pipe in the flow direction immediately behind the nozzle prevail. This ensures that an already relatively wide stream of reducing agent is introduced into the middle of the pipe of the exhaust pipe and the further distribution of the reducing agent over the entire pipe cross section is made possible on a relatively short mixing section.

Further advantages and details of the invention are explained in the patent claims and in the description and illustrated in the figures. It shows:

Figure 1 is a side view of a arranged on an exhaust pipe and projecting into the exhaust pipe into neck;

Figure 2 is a perspective view of a nozzle with a flange collar and holes in the lower channel wall portion;

Figure 3 is a plan view of an exhaust pipe with a

 Opening for a neck;

Figure 4 is a sectional view of the nozzle of FIG. 2;

Figure 4a is a detail view of the upper part of the cone according to Figure 4 with a different cutting guide;

Figure 5 is a bottom view of the nozzle according to

 Fig. 4;

Figure 6 is a perspective view of the nozzle according to

 Fig. 4.

In Fig. 1, a nozzle 2 is shown, which has a channel 21 for introducing a reducing agent into an exhaust pipe 1. The channel 21 is essentially ro- formed symmetrical and cone-shaped to its central axis 20. Into the channel 21 protrudes an injection nozzle 3, via which the reducing agent is injected into the channel 21. The injection nozzle 3 is screwed into a receptacle 26 shown in detail in FIGS. 4 and 6.

At the end of the channel 21 opposite the injection nozzle 3, the channel 21 has its largest cross-section Qk, where the reducing agent exits from the neck 2 and into the exhaust pipe 1. The nozzle 2 is made with its central axis 20 at an angle ms of about 30 ° with respect to a central flow axis 11 of the exhaust pipe 1. The middle flow axis 11 forms according to the embodiment in Fig. 1 at the same time the central axis 10 of the exhaust pipe. 1

The nozzle 2 is arranged in an opening 12 shown in Fig. 3 from above in the exhaust pipe 1. Due to the very flat arrangement of the nozzle 2 to the exhaust pipe 1, the opening 12 has an oval cross-section with a diameter Dmax which is greatest in the direction of the central flow axis 11.

The nozzle 2 is placed on the exhaust pipe 1. For this purpose, the neck 2, as shown in FIG. 2 and in FIGS. 4 to 6, has a flange collar 23 which is curved in the circumferential direction around the peripheral surface 13 of the exhaust pipe 1 and completely surrounds the opening 12 of the exhaust pipe 1. With the flange collar 23, which is curved parallel to the exhaust pipe 1 about a coaxial with the central axis 10 arranged axis 27, the nozzle 2 is adjusted relative to the exhaust pipe 1 and welded to the exhaust pipe 1 or soldered. The nozzle 2 protrudes in the direction of the central axis 20 at different positions in the circumferential direction about the channel 21 more or less far into the exhaust pipe 1 into it. With a channel wall section 21a on the underside of the channel 21, a maximum length Lmax is given in the direction of the channel wall 24, around which the channel 21 projects into the exhaust pipe 1. This channel wall section 21a protrudes downwards in the radial direction over the central flow axis 11 by more than 50% of a diameter Da of the exhaust gas line 1 into the exhaust gas line 1.

Due to the described geometry, the length Lmax is greater than the maximum diameter Dmax of the opening 12. The channel 21 thus begins in the direction of gravity down in the direction of the nozzle 2 opposite inner wall of the exhaust pipe 1 oriented droplets of the reducing agent. Due to the temperature of the nozzle 2, the reducing agent evaporates and crystallization at the exhaust pipe 1 is prevented.

The orientation of the channel 21, which is flat relative to the exhaust pipe 1, also causes the reducing agent to be less deflected from an injection direction E into a flow direction S of the exhaust gas, thus reducing the flow-related influences on the preferred distribution in the exhaust pipe 1 on the side of the reducing agent , At the same time, a distribution of the reducing agent over a majority of the cross-sectional area Qa of the exhaust pipe 1 is already achieved centrally in the channel 21 by the large cross-sectional area Qk of the channel in the outlet region relative to a cross-sectional area Qa of the exhaust pipe 1. In the flow direction S, therefore, a mixing element is not shown directly behind the nozzle 2. Overall, the geometry of the advantages of a wide range injected in the edge region of the exhaust pipe 1 cone of reducing agent and a centrally injected into the exhaust pipe 1 via a lance jet of reducing agent can be combined, because of the nozzle 2 wide diversified cone of reducing agent in the center of the pipe is introduced.

The channel 21, which projects into the exhaust pipe 1, has, according to FIGS. 2, 4 to 6, irregularly distributed holes 25, 25a which, with their drilling axis, follow a pattern of special flow vectors theoretically and / or practically detected in the channel 21 are aligned at different angles. The holes 25, 25 a are arranged mirror-symmetrically to a plane which is spanned by the two central axes 10, 20.

The channel 21 is formed of cast iron with a wall thickness 28 of at least 3.3 mm. Through holes 25, 25 a, which have a length LI (Figure 4a) of several millimeters due to the wall thickness 28, a kind of nozzles are formed which generates on the inner surface of the channel 21 there flows in the direction of the exhaust pipe 1, where previously without such holes Flows in the direction of the injection nozzle 3 prevail, which could be mapped with flow vectors with at least one component in the direction of the injection nozzle 3. Characterized in that a portion of the exhaust gas is passed through the holes 25, 25a in the channel 21, the channel 21 is heated from the inside by the exhaust gas. The increased temperature in the channel 21 also reduces the crystallization of the reducing agent.

The holes 25, 25 a are in the radial direction to the central axis 20 in accordance with the previously determined vector image or aligned at an angle b to the radial direction. According to the embodiments of FIGS. 4 to 6, a total of 20 holes 25, 25a are arranged. The channel 21 is in the region of the channel wall portion 21a below the central axis 20 free of holes 25, whereby deposits of the reducing agent on the channel 21 opposite side of the exhaust pipe 1 are avoided.

1, 4 to 6, a spoiler 22 is sketched, which is arranged in the flow direction of the exhaust gas after the upper two holes 25 a on the channel 21. With the spoiler 22, a portion of the exhaust gas flow is actively branched off and directed to rinse the channel 21 in the upper region in the respective hole 25 a. The concave half-shell-shaped or semicircular-shaped spoiler 22 (FIGS. 5 and 6), which is concave in the flow direction, is shown in this sectional drawing only in a quarter-circle. This quarter-circle-shaped cross-section of the spoiler 22 is shown by a dashed line 22a. The one of four holes 25a shown in more detail in FIG. 4a forwards the exhaust gas stream branched off through the spoiler 22 into the upper region of the channel 21.

Claims

claims Connecting piece (2) for arranging on an opening (12) of an exhaust gas line (1) carrying an exhaust gas flow with a central axis (10) and for flanging an injection nozzle (3) for a reducing agent, wherein the socket (2) has an opening around its central axis (20 ) circulating, the reducing agent in the exhaust pipe (1) leading channel (21) which projects into the exhaust pipe (1) and the nozzle (2) at least partially around the channel (21) circumferential flange collar (23), characterized characterized in that Flange collar (23) about a, to the central axis (10) of the exhaust pipe (1) to be coaxially arranged axis (27), parallel to the peripheral surface (13) of the exhaust pipe (1) is curved and the nozzle (2) with the flange collar (23) medium - Or directly on the exhaust pipe (1) can be placed. Stub (2) according to claim 1, characterized in that between the central axis (20) and the axis (27) an angle ms between 25 ° and 65 ° is formed. Stub (2) according to claim 1 or 2, characterized in that the channel (21) in the radial direction to the axis (27) by at least 30% of a diameter Da of the exhaust pipe (1) into the exhaust pipe (1) protrudes into it. Stub (2) according to one of the preceding claims, characterized in that in the exhaust pipe (1) projecting channel (21) has a channel wall portion (21 a) which in the direction of a channel wall (24) has a length Lmax which is at least 80% a maximum diameter Dmax of the opening (12). Stub (2) according to one of the preceding claims, characterized in that in the exhaust pipe (1) projecting channel (21) regularly or irregularly distributed holes (25, 25a), which can be detected by a in the channel (21) pattern of special Flow vectors of the flow are arranged. Stub (2) according to claim 5, characterized in that the holes (25, 25a) are aligned in the radial direction to the central axis (20) or at an angle b to the radial direction. Nozzle (2) according to one of the preceding claims, characterized in that at least the channel (21) is designed as a casting with a wall thickness (28) between 2.4 mm and 5.3 mm, wherein the holes (25, 25a) each after alignment nozzles with a length (LI) between 2.4 mm and 6, 8 mm form. Stub (2) according to claim 4 to 7, characterized in that the channel (21) in the region of the portion (21a) is vertically below the central axis (20) free of holes (25). 9. nozzle (2) according to any one of the preceding claims, characterized in that in the flow direction (S) of the exhaust gas after one or more holes (25 a) a spoiler (22) on the channel (21) is arranged, with which a part of the exhaust gas stream can be branched off from a central flow axis (11) and directed into the respective hole (25). 10. nozzle (2) according to claim 8, characterized in that the spoiler (22) opposite to the flow direction is concave and in the flow direction in front of the spoiler (22) at least two holes are arranged. 11. nozzle (2) according to any one of the preceding claims, characterized in that a cross-sectional area Qk of the channel (21) at the end of the nozzle (2) in the exhaust pipe (1) between 30% and 80% of a cross-sectional area Qa of the exhaust pipe (1 ) corresponds. 12. nozzle (2) according to any one of the preceding claims with an exhaust system for commercial vehicles, wherein the exhaust system comprises at least one SCR catalyst and a silencer and optionally a particulate filter and / or manifold pipes and / or a turbocharger.