Apparatus For Mixing An Additive With A Gas Flow

Abstract

The present invention relates to an apparatus for mixing an additive with a gas flow, in particular for an exhaust gas system of a vehicle having an internal combustion engine, that comprises a mixing chamber which can be flowed through by at least a portion of the gas flow, said mixing chamber having at least one inlet opening through which a main inlet flow of the gas flow flows into the mixing chamber on operation of the apparatus, having at least one metering opening and having at least one outlet opening. The apparatus further comprises a metering device by means of which an additive flow of the additive can be introduced into the mixing chamber through the metering opening, wherein the inlet opening and the metering opening are arranged and formed such that the main inlet flow and the additive flow in substantially opposite directions into the mixing chamber so that the main inlet flow and the additive flow impact one another.

Claims

1. An apparatus for mixing an additive with a gas flow, said apparatus comprising a mixing chamber which can be flowed through by at least a portion of the gas flow, said mixing chamber having at least one inlet opening through which a main inlet flow of the gas flow flows into the mixing chamber on operation of the apparatus, having at least one metering opening and having at least one outlet opening; and a metering device by means of which an additive flow of the additive can be introduced into the mixing chamber through the metering opening, wherein the inlet opening and the metering opening are arranged and formed such that the main inlet flow and the additive flow flow in substantially opposite directions into the mixing chamber so that the main inlet flow and the additive flow impact one another.

2. The apparatus in accordance with claim 1, wherein the inlet opening and the metering opening are arranged at mutually oppositely disposed wall sections of the mixing chamber.

3. The apparatus in accordance with claim 1, wherein the inlet opening is designed as substantially round or rectangular.

4. The apparatus in accordance with claim 1, wherein a center axis of the main inlet flow and a center axis of the additive flow are arranged substantially coaxially, or wherein a center axis of the additive flow lies in a center plane of the main inlet flow.

5. The apparatus in accordance with claim 4, wherein the outlet opening of the mixing chamber is arranged at a wall section that, viewed in the direction of the center axis of the main inlet flow or of the additive flow, is disposed between the metering opening and the inlet opening.

6. The apparatus in accordance with claim 4, wherein the outlet opening of the mixing chamber forms a gas outlet of the apparatus.

7. The apparatus in accordance with claim 1, wherein the mixing chamber is circular or rectangular in a plane perpendicular to the center axis of the main inlet flow and of the additive flow.

8. The apparatus in accordance with claim 1, wherein at least one wall section of the mixing chamber having the inlet opening is designed as at least sectionally curved.

9. The apparatus in accordance with claim 8, wherein the at least one wall section adjacent to the inlet opening is designed in U shape.

10. The apparatus in accordance with claim 1, wherein wall sections disposed between the inlet opening and the metering opening are at least sectionally curved.

11. The apparatus in accordance with claim 1, wherein the mixing chamber has at least one secondary opening through which a secondary inlet flow of the gas flow flows into the mixing chamber on operation of the apparatus.

12. The apparatus in accordance with claim 11, wherein the secondary opening is associated with at least one flow-conducting section that is designed and arranged such that the secondary inlet flow is deflected when entering into the mixing chamber.

13. The apparatus in accordance with claim 12, wherein the least one flow-conducting section is a planar and/or a curved wall section.

14. The apparatus in accordance with claim 1, wherein the metering device is associated with a screening device that has at least one flushing opening through which a portion of the gas flow passes as a flushing flow into an injection region of the metering device.

15. The apparatus in accordance with claim 14, wherein the flushing opening is associated with a flow-conducting unit.

16. The apparatus in accordance with claim 1, wherein the mixing chamber is at least sectionally surrounded by a housing that has a gas inlet for the gas flow, wherein the interior of the mixing chamber is in communication with the interior of the housing at least via the inlet opening.

17. The apparatus in accordance with claim 16, wherein the outlet opening of the mixing chamber is in communication with a channel through which the gas flow exiting from the mixing chamber is discharged from the housing.

18. The apparatus in accordance with claim 17, wherein the channel at least sectionally surrounds the mixing chamber at an outer side in a region between the metering opening and the inlet opening in a peripheral direction.

19. The apparatus in accordance with claim 18, wherein the channel completely surrounds the mixing chamber.

20. The apparatus in accordance with claim 16, wherein the metering device is supported by the housing and is arranged spaced apart from the inlet opening.

21. The apparatus in accordance with claim 16, wherein a gap is at least sectionally formed between the mixing chamber and the housing and, during operation, is flowed through by at least a portion of the gas flow entering the housing through the gas inlet.

22. The apparatus in accordance with claim 21, wherein at least one gas-conducting component is arranged in the gap or in the direction of flow upstream of the gap in order to influence the gas flow in the gap and/or into the gap.

23. The apparatus in accordance with claim 17, wherein the metering opening is arranged and designed such that a portion of the gas flow in the housing flows as a backflow together with the additive flow through the metering opening into the mixing chamber.

24. The apparatus in accordance with claim 23, wherein a flow-conducting device is provided that is configured to influence the backflow prior to the entry into the metering opening.

25. The apparatus in accordance with claim 24, wherein the flow-conducting device comprises a separate component and/or wherein the flow-conducting device is formed by at least one component that—if provided—is formed at the screening device and/or at the mixing chamber.

26. The apparatus in accordance with claim 25, wherein the at least one component is formed in the form of a collar formed at—if provided—the screening device and/or at the mixing chamber.

27. The apparatus in accordance with claim 14, wherein the apparatus is designed such that, during operation, the main inlet flow portion of the gas flow is greater than the portion of the backflow and/or the portion of the backflow is greater than the portion of the flushing flow, wherein the main inlet flow makes up 70% to 30, and/or the backflow makes up 60% to 30, and/or the flushing flow makes up 20% to 1% of the gas flow.

28. The apparatus in accordance with claim 1, wherein the apparatus further comprises at least one further metering device by means of which a further additive flow of the additive can be introduced into the mixing chamber through the metering opening of the mixing chamber or through a further metering opening of the mixing chamber, wherein the inlet opening and the metering opening or the further metering opening are arranged and formed such that the main inlet flow and at least one of the additive flows flow in substantially opposite directions into the mixing chamber so that the main inlet flow and the additive flow impact one another.

29. An exhaust gas system that comprises an apparatus for mixing an additive with a gas flow, said apparatus comprising a mixing chamber which can be flowed through by at least a portion of the gas flow, said mixing chamber having at least one inlet opening through which a main inlet flow of the gas flow flows into the mixing chamber on operation of the apparatus, having at least one metering opening and having at least one outlet opening; and a metering device by means of which an additive flow of the additive can be introduced into the mixing chamber through the metering opening, wherein the inlet opening and the metering opening are arranged and formed such that the main inlet flow and the additive flow flow in substantially opposite directions into the mixing chamber so that the main inlet flow and the additive flow impact one another.

30. A vehicle comprising an internal combustion engine that is connected to an exhaust gas system that comprises an apparatus for mixing an additive with a gas flow, said apparatus comprising a mixing chamber which can be flowed through by at least a portion of the gas flow, said mixing chamber having at least one inlet opening through which a main inlet flow of the gas flow flows into the mixing chamber on operation of the apparatus, having at least one metering opening and having at least one outlet opening; and a metering device by means of which an additive flow of the additive can be introduced into the mixing chamber through the metering opening, wherein the inlet opening and the metering opening are arranged and formed such that the main inlet flow and the additive flow flow in substantially opposite directions into the mixing chamber so that the main inlet flow and the additive flow impact one another.

Description

[0044] The invention will be described in the following only by way of example with reference to embodiments and to the drawings. There are shown:

[0045] FIG. 1A shows a schematic representation of an embodiment of the apparatus in accordance with the invention;

[0046] FIG. 1B shows a schematic representation of a further embodiment of the apparatus in accordance with the invention;

[0047] FIG. 2 shows a perspective representation of an inlet side of a cylindrical embodiment of the apparatus in accordance with the invention;

[0048] FIG. 3 shows a perspective representation of an outlet side of the embodiment of FIG. 2;

[0049] FIG. 4A shows a sectional representation of the embodiment of FIG. 2;

[0050] FIG. 4B shows a schematic representation of the distribution of the additive flow at a relatively high inflow speed of the main inlet flow of the embodiment of FIG. 2;

[0051] FIG. 4C shows a schematic representation of the distribution of the additive flow at a relatively low inflow speed of the main inlet flow of the embodiment of FIG. 2;

[0052] FIG. 5 shows a perspective representation of the embodiment of FIG. 2 without a housing;

[0053] FIGS. 6 and 7 show different sections of the embodiment of FIG. 2;

[0054] FIGS. 8 and 9 show different sections of a slightly modified embodiment of FIG. 2;

[0055] FIG. 10 shows a perspective representation of an inlet side of a spherical embodiment of an apparatus in accordance with the invention;

[0056] FIG. 11 shows a sectional representation in a side view of the spherical embodiment of FIG. 10; and

[0057] FIG. 12 shows a plan view of the spherical embodiment of FIG. 10 with alternative outlet pipe arrangements.

[0058] A schematic representation of an apparatus 100 for mixing an additive with a gas flow, for example an exhaust gas flow, is shown in FIG. 1A. It can be integrated into an exhaust gas purification device or connected upstream of such a device by which exhaust gases of an internal combustion engine are purified by means of an SCR process, among other things.

[0059] The apparatus 100 comprises a mixing chamber 102 and a metering device 104. The mixing chamber 102 can be flowed through by at least a portion of a gas flow at least has an inlet opening 108, a metering opening 112, and an outlet opening 114 (not shown in FIG. 1A, see, for example, FIG. 3). A main inlet flow 106 of the gas flow flows into the mixing chamber 102 through the inlet opening 108 on operation of the apparatus 100. An additive flow 110 of an additive is introduced into the mixing chamber 102 through the metering opening 112 by means of the metering device 104 on operation of the apparatus 100. The metering device 104 can be attached to the chamber 102.

[0060] The inlet opening 108 and the metering opening 112 are arranged and formed such that the main inlet flow 106 and the additive flow 110 flow in substantially opposite directions into the mixing chamber 102 so that the main inlet flow 106 and the additive flow 110 impact one another in the mixing chamber 102. In this connection, the term “substantially” is to be understood such that the directions of flow of the main inlet flow 106 and the additive flow 110 indeed have opposite directions (impact flow), but do not have to be aligned strictly in parallel with or coaxially to one another, which would correspond to an angle of 180° between the flows. A deviation of the center axis B of the additive flow 110 from the center axis A of the main inlet flow 106 can amount to between +45° and −45° (corresponding to an angle between the center axes A, B of 215° or 135°), in particular between +20° and −20°, preferably between +10° and −10°, and particularly preferably between +5° and −5°. Due to the opposite directions of flow of the main inlet flow 106 and the additive flow 110, the two flows impact one another in the mixing chamber 102. By controlling/regulating the metering device 104, the flow 110 can be adapted to the flow 106 to ensure their impacting in a suitable region in the interior of the chamber 102.

[0061] The mixing chamber 102 has a first side 116 and a second side 120 that are disposed opposite one another. The first side 116 comprises a first wall section 118 at which the inlet opening 108 of the mixing chamber 102 is arranged. The second side 120 comprises a second wall section 122 at which the metering opening 112 of the mixing chamber 102 is arranged. Curved sections can in particular also be provided at marginal regions of the first wall section 118 or the second wall section 122. The mixing chamber 102 furthermore has at least one lateral wall section 124 that connects the first wall section 118 and the second wall section 122 and that is arranged between the first side 116 and the second side 120 of the mixing chamber 102. The first wall section 118, the second wall section 122, and/or the lateral wall section 124 can be planar or curved, wherein curved wall sections 118, 122, 124 can assist a swirl formation of the gas flows in the interior of the mixing chamber 102. A lateral wall section 124 has in particular proved to be advantageous that has a kidney-shaped design in a cross-section in a plane that includes the center axis A of the main inlet flow 106 and/or the center axis B of the additive flow 110. A cross-section of the mixing chamber 102 perpendicular to the center axis A of the main inlet flow 106 and/or to the center axis B of the additive flow 110 can be rectangular or circular. However, the mixing chamber 102 can also have alternative geometries or cross-sections, such as oval or polygonal.

[0062] The metering device 104 is arranged at the second side 120 of the mixing chamber 102 and is configured to introduce an additive through the metering opening 112 into the mixing chamber 102 via an injection device, for example, via a nozzle. The additive can be injected into the mixing chamber 102 by the injection device, for example, in the form of a spray cone 126.

[0063] The main inlet flow 106 flows substantially symmetrically to the center axis A through the inlet opening 108 into the mixing chamber 102. The center axis A of the main inlet flow 106 extends approximately centrally through the inlet opening 108. The main inlet flow 106 flows toward the metering opening 112 in this respect. The additive flow 110 flows substantially symmetrically to the center axis B through the metering opening 112 into the mixing chamber 102. The center axis B of the additive flow 110 extends approximately centrally through the metering opening 112. The additive flow 110 flows toward the inlet opening 108 in this respect. The center axis A of the main inlet flow 106 and the center axis B of the additive flow 110 are coaxially arranged in the present example. In a rectangular design of the inlet opening 108, the center axis B of the additive flow 110 can lie in a center plane of the main inlet flow 106. The center plane of the main inlet flow 106 then comprises the center axis A of the main inlet flow 106 and is arranged substantially in parallel with the at least one lateral wall section 124 of the mixing chamber 102.

[0064] Due to the impacting of the main inlet flow 106 and the additive flow 110, the gaseous main inlet flow 106 and the liquid additive flow 110 mix in the mixing chamber 102. Furthermore, the direct impacting of the main inlet flow 106 with the additive flow 110 leads to a splitting, a spreading, or a division of the additive flow 110 so that the additive flow 110 is distributed in the interior of the mixing chamber 102.

[0065] The arrangement and the design of the inlet opening 108 and the metering opening 112 and the associated introduction of the additive flow 110 and the main inlet flow 106 in opposite directions into the mixing chamber 102 effects a good mixing with the additive flow 110 even with a small flow of the main inlet flow 106, for example with a small load of the internal combustion engine. A “spraying” of the additive through the mixing chamber 102, for example, with no or only little contact of the additive with the main inlet flow 106, can be largely avoided.

[0066] The flow conditions in the interior of the mixing chamber 102 depend on the properties of the mass flows 110, 106 and are load-dependent due to the usually much larger mass flow 106.

[0067] FIG. 1B shows a schematic representation of a further embodiment of the apparatus 100 in accordance with the invention in which an optional gaseous backflow 128 is additionally shown. The backflow 128, together with the additional flow 110 (droplet flow), can be introduced into the mixing chamber 102 through the metering opening 112. The backflow 128 assists the introduction of the additive flow 110 into the mixing chamber since the backflow 128 is mixed with the additive flow 110 and a gas-additive mixture produced in this manner flows into the mixing chamber 102 through the metering opening 112. In the interior of the mixing chamber 102, the main inlet flow 106 and the backflow 128 impact one another at an (idealized) stagnation point 129. Due to the impacting, the main inlet flow 106 and the gas-additive mixture are deflected such that the direction of flow of the main inlet flow 106 and the direction of flow of the backflow 128 extend substantially perpendicular to the center axis A of the main inlet flow 106 or to the center axis B of the additive flow 110 after the impact at the stagnation point 129. In other words, after their impact, the flows 106, 128 are deflected radially outwardly with respect to the center axes A, B and flow toward the lateral wall section 124. Due to the impact, the main inlet flow 106, the additive flow 110, and the backflow 128 mix and both an evaporation of the additive in the mixing chamber 102 and a mixing of the mentioned material flows take place. Due to the outward deflection of the direction of flow in the direction of the lateral wall section 124, the dwell time of the additive in the mixing chamber 102 can furthermore be increased, which in turn leads to a better evaporation of the additive. On an impacting of the deflected gas flows 106, 110, 128 on the lateral wall section 124, an evaporation of previously non-evaporated additive droplets occurs there. After the impacting of the gas flows 106, 110, 128 on the lateral wall section 124, the gas flows 106, 110, 128 are deflected again and are directed upwardly or downwardly along the lateral wall section 124 (cf. FIGS. 4A to 4C). This results in a swirling or in a swirl formation of the gas flows 106, 110, 128, which advantageously assists a further mixing and evaporation.

[0068] The location of the stagnation point 129 depends substantially on the properties of the mass flows of the main inlet flow 106 and the backflow 128 since the mass flow of the liquid additive flow 110 is usually much smaller than those of the gaseous mass flows 106, 128. If fixed geometric conditions are present, the stagnation point 129 does not shift or only shifts slightly, even under different load states of the internal combustion engine.

[0069] FIG. 2 shows a perspective representation of an inlet side 130 of an embodiment of the apparatus 100 in accordance with the invention. The mixing chamber 102 is at least sectionally surrounded by a cylindrical housing 132, wherein the housing 132 has a gas inlet at the inlet side 130. The gas inlet corresponds to the entire cross-section of the housing 132.

[0070] A gas-conducting component 134 is arranged at the inlet side 130 and is configured as a circular plate having selectively distributed openings 136 through which the gas flow can flow into a gap 138 between the housing 132 and the mixing chamber 102 (see FIG. 4).

[0071] The openings 136 of the gas-conducting component 134 are arranged in a radial marginal region. A central region of the gas-conducting component 134 forms a part of the wall section 124. In a region adjacent to the inlet opening 108 of the mixing chamber 102, no opening 136 is provided in the gas-conducting component 134. It is thereby prevented that at least a portion of the gas flow flows into the opening 108 without a substantial deflection so that it cannot flow directly into the mixing chamber 102. The openings 136 are designed such that the gas flow flowing into the gap 138 through the openings 136 is deflected and divided, namely into a comparatively small part flow that flows to the metering device 104, into a slightly larger part flow that passes to the metering opening 112, and into a comparatively large part flow that flows toward the inlet opening 108. Due to its inflow, the gas flow furthermore heats the gas-conducting component 134 and thus the lateral wall section 124 of the mixing chamber 102.

[0072] FIG. 3 shows a perspective representation of an outlet side 140 of the embodiment described in FIG. 2. An outlet opening 114 in an axial wall 144, which likewise forms a part of the wall section 124 of the mixing chamber 102, has a spectacle-shaped cross-section, for example in the form of an eight lying on its side, wherein the cross-section of the outlet opening 114 is smaller than the cross-section of the mixing chamber 102. A gas flow flowing into the housing 132 and then into the mixing chamber 102 can only exit from the mixing chamber 102 via the outlet opening 114. Thus, the outlet opening 114 of the mixing chamber 102 forms a gas outlet of the apparatus 100. The housing 132 itself does not have a gas outlet.

[0073] FIG. 4A shows a sectional representation of the embodiment described in FIG. 2. The mixing chamber 102 is bounded by the first wall section 118, the second wall section 122, and the lateral wall section 124. In the described cylindrical embodiment of the apparatus 100, the mixing chamber 102 in each case has two first wall sections 118, two second wall sections 122, and two lateral wall sections 124 (formed by portions of the component 134 or of the wall 144). The first wall sections 118 of the mixing chamber 102, which are separated by the inlet opening 108, are each at least sectionally designed as concavely curved, in particular in the shape of a flat U. They thereby develop a funnel effect for the inlet opening 108.

[0074] The metering opening 112 is arranged and designed such that a portion of the gas flow in the housing 132 flows as a backflow 128 together with the additive flow 110 through the metering opening 112 into the mixing chamber 102. The metering device 104 is supported by the housing 132 and is arranged spaced apart from the inlet opening 108.

[0075] However, in other embodiments, the first wall sections 118 can also be curved in a different manner. The curvature of the first wall sections 118 can assist a swirl formation of the gas flows in the interior of the mixing chamber 102. The first wall sections 118 can in particular act as a kind of deflector that directs a stagnation flow, which is produced due to the flows 106, 110, 128 (incoming main inlet flow 106, incoming additive flow 110 flowing in the opposite direction to the main inlet flow 106, and backflow 128) meeting at the stagnation point 129, along the curved surface of the first wall sections 118 in the direction of the metering opening 112 again. The lateral wall sections 124 disposed between the inlet opening 108 and the metering opening 112 are likewise at least sectionally curved. The curvatures of the individual wall sections 118, 122, 124 are adapted to the conditions to be expected on operation of the apparatus 100 in order to produce a swirl structure or a vortex structure in the interior of the mixing chamber 102.

[0076] Between the housing 132 and the mixing chamber 102, the gap 138 is at least sectionally formed, said gap 138 being flowed through by at least a portion of the gas flow entering into the gap 138 through the gas inlet, in particular through the openings 136 of the gas-conducting component 134 (cf. FIG. 2), on operation of the apparatus 100. The gas-conducting component 134 therefore serves to influence the gas flow in the gap 138 and/or into the gap 138. Further components can be arranged in the gap 138, as required, to design the flow pattern.

[0077] A flow-conducting device 142 described in more detail below is arranged between the gap 138 and the metering opening 112. It influences the formation of the backflow 128. A collar 123 that is formed at the wall section 122 and that projects into the interior of the mixing chamber 102 facilitates the inflow of the backflow 128 into the chamber 102. The collar 123 also deflects gas flowing along the wall section 124 into the interior of the mixing chamber 102 again in order to assist the swirl formation or vortex formation.

[0078] The metering device 104 is protected from a direct inflow of gas by a flow-conducting unit 154, which will be explained in more detail below. A screening metal plate 145 having a collar 143 projecting toward the metering device 104 is furthermore provided. Lateral marginal sections 145A of the screening metal plate 145 prevent a lateral outflow of gas from the metering-in region into the gap 138, and vice versa (see FIG. 5).

[0079] The interior of the mixing chamber 102 is in communication with the interior of the housing 132 at least via the inlet opening 108. In the interior of the mixing chamber 102, the main inlet flow 106 and the additive flow 110 impact one another on operation of the apparatus 100, wherein the additive flow 110 flows together with the backflow 128 through the metering opening 112 into the mixing chamber 102 and the main inlet flow 106 flows through the inlet opening 108 into the mixing chamber 102. A resulting stagnation flow enables a large-area distribution of the gas-additive mixture within the mixing chamber 102. The bounding wall sections 118, 122, 124 of the mixing chamber 102, i.e. the first wall sections 118, the second wall sections 122 and the lateral wall sections 124, serve as evaporator metal sheets and are flowed around at an outer side by the exhaust gas flow flowing through the openings 136 into the gap 138 and are thus heated, whereby an improvement in the evaporation of the additive mixture is achieved in the interior of the mixing chamber 102.

[0080] The formation of the flow pattern of the flows 106, 110, 128 produced in the interior of the chamber 102 also depends—in addition to the geometric design of the components of the apparatus 100—on the operating state, i.e. on the properties of the gas flow (which in turn depends on the load state of the internal combustion engine) and on the metering-in characteristics of the additive. This will be explained with reference to the following Figures.

[0081] FIG. 4B shows, in addition to FIG. 4A, a schematic representation of the distribution of the additive flow 110 in the mixing chamber 102 at a relatively high inflow speed of the main inlet flow 106. When the main inlet flow 106 flows into the mixing chamber 102 at a relatively high speed, the additive flow 110 is deflected together with the backflow 128 in the direction of an impact surface 152, wherein the impact surface is arranged at an upper wall section 124, in the vicinity of the metering opening 112.

[0082] In contrast to FIG. 4B, FIG. 4C shows a schematic representation of the distribution of the additive flow 110 in the mixing chamber 102 at a relatively low inflow speed of the main inlet flow 106. When the main inlet flow 106 flows into the mixing chamber 102 at a relatively low speed, the additive flow 110 is deflected together with the backflow 128 in the direction of an impact surface 152, wherein the impact surface is arranged at a lower wall section 124, in the vicinity of the inlet opening 108.

[0083] The location of the stagnation point 129 remains substantially constant and is independent of the inflow speed of the main inlet flow 106 since the main inlet flow 106 and the backflow 128 are—as explained—substantially dependent on the geometric conditions (e.g. on the ratio of the size and/or on the design of the openings for the main inlet flow 106 and the backflow 128) and are therefore in a fixed relationship to one another. Regardless of the inflow speed of the main inlet flow 106, the stagnation flow that is being formed in the interior of the mixing chamber 102 results in an efficient evaporation of the additive flow 110 since the stagnation flow deflects the additive flow 110 radially outwardly onto the evaporator surfaces and the geometric design of the evaporator surfaces results in a swirl formation of the stagnation flow in the interior of the mixing chamber 102, and the dwell time of the additive flow 110 in the mixing chamber 102 is thus extended.

[0084] FIG. 5 shows a perspective representation of the embodiment of FIG. 2 without a housing 132. The gas flow flowing in at the inlet side 130 of the apparatus 100 through the openings 136 of the gas-conducting component 134 is split into the main inlet flow 106 and the backflow 128, among others. The main inlet flow 106 flows into the mixing chamber 102 through the inlet opening 108. The backflow 128 flows into the mixing chamber 102 through the metering opening 112 that is preceded by the flow-conducting device 142. In the present example, the flow-conducting device 142 is a regionally perforated (separate) sheet metal part. The design of the perforation bounds the backflow 128.

[0085] The two oppositely introduced flows 106, 128 impact one another in the mixing chamber 102 and form the stagnation flow that has already been described multiple times and that leads to the formation of a complex swirl structure or vortex structure in cooperation with the geometric design of the mixing chamber 102.

[0086] FIG. 6 shows a sectional representation of the embodiment of FIG. 2 in a plane that is perpendicular to the center axis B of the additive flow 110, wherein a view from the interior of the mixing chamber 102 in the direction of the metering device 104 is shown. The mixing chamber 102 is bounded in the longitudinal direction, i.e. perpendicular to the flow axis C of the gas flow, by the gas-conducting component 134 at the inlet side 130 and by the axial wall 144 at the outlet side 140. Said gas-conducting component and said axial wall are inserted into the cylindrical housing 132. The wall sections 118, 122, 124 forming the chamber 102 are arranged between the plate-like components 134, 144. Said wall sections are formed at two substantially identical curved sheet metal parts (one to the right of axis C, one to the left thereof) that are spaced apart from one another so that the first wall sections 118 and the second wall sections 122 form the rectangular openings 108 or 112 (see also FIG. 7).

[0087] FIG. 7 shows a further sectional representation of the embodiment of FIG. 2 in a plane that is perpendicular to the center axis A of the main inlet flow 106, wherein a view from the interior of the mixing chamber 102 in the direction of the inlet opening 108 is shown. As already mentioned above, the inlet opening 108 formed by the first wall section 118 is designed as substantially rectangular in this embodiment. The inlet opening 108 is formed smaller than the metering opening 112 in the present case. Thus, at a constant exhaust gas counter-pressure, a higher inflow speed of the main inlet flow 106 can be achieved compared to an inflow speed of the backflow 128.

[0088] FIG. 8 shows a sectional representation of the embodiment of FIG. 2 in a plane that includes the center axis B. The gas flow flowing into the housing 132 through the openings 136 of the gas-conducting components 134 enters the mixing chamber 102 through the metering opening 112 after passing through the flow-conducting device 142. The flow-conducting device 142 serves to influence the backflow 128 prior to entering the metering opening 112. It also acts as a screen of the spray cone 126. A further function of the flow-conducting device 142 can be an additional swirl generation in the backflow 128. A backflow 128 impacted by swirl can contribute towards a stabilization of the spray cone 126. Unlike shown, planar and/or curved guide surfaces can be provided that effect such a swirl formation. If required, a (partial) mixing of the backflow 128 with the additive flow 110 can also be provided in the mixing chamber 102.

[0089] It can also be seen in FIG. 8 that the flow-conducting unit 154 has a collar 143A that projects into the collar 143 of the screening metal plate 145.

[0090] FIG. 9 shows a representation of the apparatus 100 of FIG. 2 in a section through the flow-conducting unit 154 with swirl generation (preferably a separate sheet metal part) in a plane perpendicular to the center axis B. In this embodiment, the flow-conducting unit 154 is designed as circular and has flow-conducting surfaces 162 that are arranged distributed in a peripheral direction and that are each associated with a flushing opening 158. The flow-conducting surfaces 162 are sections that are bent from a jacket surface of the flow-conducting unit 154 and that extend into the interior of the flow-conducting unit 154. A gas flow that flows at the inlet side 130, in particular through the openings 136 of the gas-conducting component 134, into the housing 132 is partly conducted in the direction of the metering device 104 through one of the openings 136. This gas portion then flows as a flushing flow through the flow-conducting unit 154 to the metering device 104. In this respect, the flushing flow is set into a swirling movement or a rotational movement about the center axis B of the additive flow 110 by the flow-conducting surfaces 162 before the flushing flow impacts the additive flow 110. The flushing flow prevents the formation of deposits in the region of a nozzle of the metering device 104. Such flow-conducting surfaces 162 are not provided in the embodiment in accordance with FIG. 2, which can be easily recognized with reference to FIG. 5.

[0091] FIG. 10 shows a perspective representation of an inlet side 130 of a further embodiment of the apparatus 100 in accordance with the invention. FIG. 11 shows a section through the same.

[0092] The mixing chamber 102 has a toroidal basic shape and comprises a plurality of outlet openings 114 (see FIG. 11) that are in communication with a channel 146 that surrounds the mixing chamber 102 in a peripheral direction. Said channel is formed by an annular sheet metal shell that is fastened to the at least sectionally straight sidewall section 124 and that covers the outlet openings 114.

[0093] The channel 146 has an outlet 164 that is in turn connected to an outlet pipe 166. The gas flow that previously flowed completely through the mixing chamber 102 exits the apparatus 100 through the outlet pipe 166.

[0094] The mixing chamber 102 comprises a plurality of secondary openings 148 which are preferably distributed in a regular manner in a peripheral direction and through which a secondary inlet flow 156 of the gas flow flows into the mixing chamber 102 on operation of the apparatus 100. Each secondary opening 148 is associated with at least one flow-conducting section 150 that is designed and arranged such that the secondary inlet flow 156 is deflected when entering into the mixing chamber 102, in the example shown, into the curved wall sections 118. The secondary inlet flow 156 flowing into the mixing chamber 102 through the secondary openings 148 causes a back flushing of the main inlet flow 106, which can result in an acceleration of the main inlet flow 106. The at least one flow-conducting section 150 can in particular be designed as a planar and/or a curved wall section such that a perpendicular inflow of the secondary inlet flow 156, i.e. an inflow orthogonal to a wall section of the mixing chamber 102, into the mixing chamber 102 is prevented. The flow-conducting sections 150 can produce a gas flow with an additional swirl component and/or can amplify swirl components that are already present. Pressure losses in the mixing chamber 102 can furthermore be reduced by the secondary openings 148.

[0095] The metering device 104 is associated with a screening device 152 (e.g. a sheet metal part) that is preferably formed separately and that has a plurality of flushing openings 158 through which a portion of the gas flow passes as a flushing flow into an injection region of the metering device 104 and protects the latter from the formation of deposits. The screening device 152 comprises a collar 143B that projects in the direction of the mixing chamber 102.

[0096] A flow-conducting unit 154 (with or without swirl generation) is furthermore provided that is arranged between the screening device 152 and the mixing chamber 102.

[0097] The flow-conducting unit 154 with swirl generation can be formed as a separate cast component and comprises flow-conducting surfaces 162 that act as swirl flaps to generate a rotation of the backflow 128 flowing through the flow unit 154 about the center axis B of the additive flow 110. The backflow 128 rotating about the center axis B of the additive flow 110 impacts the collar 143B of the screening device 152, whereby the backflow 128 is deflected into the interior of the mixing chamber 102. The collar 143B simultaneously protects the spray cone 126 from an excessive dispersal.

[0098] FIG. 12 shows a plan view of the spherical embodiment of FIG. 10 with alternatively arranged outlet pipes 166 (shown by dashed lines). The spherical embodiment of the apparatus 100 offers the advantage that the outlet pipe 166 can be arranged at any desired outlet side 140 of the apparatus 100 depending on the installation position of the apparatus 100 in an exhaust gas system.

[0099] A common feature of the embodiments described is that an impact flow is generated in the respective device and mixes an introduced additive, for example a urea solution, with a gas flow (e.g. an exhaust gas flow). Optionally, a backflow 128 can be provided that is introduced into the mixing chamber 102 with the additive flow 110, whereby a stagnation flow is produced. In this respect, the material flows are urged radially outwardly so that the already partly mixed flows flow toward an evaporator surface that can be comparatively large. The impact flow and/or the stagnation flow can be embedded in a vortex structure that is produced by the design of the mixing chamber 102 and that improves a mixing of the (evaporated) additive with the gas flow. The functionality of the apparatus 100 is also given at comparatively small exhaust gas mass flows. A high droplet evaporation can also be achieved with a smaller exhaust gas flow and little dispersal of the drop-shaped additive. Accordingly, advantages of the apparatus 100 in accordance with the invention are an efficient evaporation of the additive and its reliable mixing with the gas flow over a large load range. Due to the apparatus 100 in accordance with the invention, advantages in terms of installation space furthermore result, for example, due to the possibility of designing said apparatus 100 in a modular manner and/or adapting it to the respective present conditions with only a small design effort.

[0100] The details explained by way of example with reference to the embodiments described above can be combined in a variety of ways to achieve the desired flow conditions.

REFERENCE NUMERAL LIST

[0101] 100 apparatus [0102] 102 mixing chamber [0103] 104 metering device [0104] 106 main inlet flow [0105] 108 inlet opening [0106] 110 additive flow [0107] 112 metering opening [0108] 114 outlet opening [0109] 116 first side of the mixing chamber [0110] 118 first wall section [0111] 120 second side of the mixing chamber [0112] 122 second wall section [0113] 123 collar [0114] 124 lateral wall section [0115] 126 spray cone [0116] 128 backflow [0117] 129 stagnation point [0118] 130 inlet side [0119] 132 housing [0120] 134 gas-conducting component [0121] 136 opening [0122] 138 gap [0123] 140 outlet side [0124] 142 flow-conducting device [0125] 143, 143A, 143B collar [0126] 144 axial wall [0127] 145 screening metal plate [0128] 145A marginal section [0129] 146 channel [0130] 148 secondary opening [0131] 150 flow-conducting section [0132] 152 screening device [0133] 154 flow-conducting unit [0134] 158 flushing opening [0135] 162 flow-conducting surface [0136] 164 outlet [0137] 166 outlet pipe [0138] A center axis of the main inlet flow [0139] B center axis of the additive flow [0140] C flow axis of the gas flow