CHAMBER MIXER FOR AN EXHAUST AFTER-TREATMENT SYSTEM OF A MOTOR VEHICLE

Abstract

The invention relates to a chamber mixer (10) for an exhaust after-treatment system of a motor vehicle, wherein a first fluid (12) can flow through the internal volume (18) of the chamber mixer in a through-flow direction (26), said internal volume being delimited by a housing (16), wherein at least one housing side of the housing (16) is double-walled and has an outer wall (30) and an inner wall (32) which divides the internal volume (18) into an inner chamber (34) and an outer chamber (36), wherein the fluid flowing in through an inlet opening (22) can be separated into a main flow (38) flowing through the inner chamber (34) and an auxiliary flow (40) flowing through the outer chamber (36), wherein the main flow (38) can be acted upon by means of a flow device (48) with a double swirl (50) and with a fluid introduction device (56) with an introduction end (58) which is arranged in the outer chamber (36) and via which a second fluid (14) can be injected into the inner chamber (34) through an introduction opening (60) in the inner wall (32).

Claims

1. Chamber mixer (10) for an exhaust after-treatment system of a motor vehicle, wherein a first fluid (58) can flow through the internal volume (14), which is delimited by a housing (12), from an inlet opening (18) arranged at one end of the internal volume (14) in the housing (12) to an outlet opening (20) arranged at the other end of the internal volume (14) in the housing (12) in a through-flow direction (22), and at least a second housing side (80) of the housing (12) is of double-walled design with an outer wall (24) and an inner wall (26), which divides the internal volume (14) into an inner chamber (28) and an outer chamber (30) located between the inner wall (26) and the outer wall (24), and the first fluid (58) flowing in through the inlet opening (18) can be divided into a main flow (54) flowing through the inner chamber (28) and an auxiliary flow (56) flowing through the outer chamber (30), and a flow device (32) is provided, by means of which the main flow (54) can be subjected to a double swirl (70) in the through-flow direction (22) and with a fluid introduction device (34) with an introduction end (36), which is arranged in the outer chamber (30) and via which a second fluid (38) can be injected into the inner chamber (28) through an introduction opening (40) in the inner wall (26), and a merging device (42) is provided downstream in the direction of flow (22), through which the main flow (54) and the auxiliary flow (56) can be guided into one another.

2. Chamber mixer (10) according to claim 1, characterized in that the flow device (32) comprises a double swirl plate (44) arranged in a first partial inlet opening (60) of the inlet opening (18).

3. Chamber mixer (10) according to claim 1, characterized in that the flow device (32) has at least one deflection element (46) arranged in the inner chamber (28) and/or on the inner wall (26) and/or at least a part of the inner wall (26) is designed as a deflection element (6).

4. Chamber mixer (10) according to claim 1, characterized in that the merging device (42) comprises at least one through-hole opening (48) at a part of the inner wall (26) associated with the outlet opening (20).

5. Chamber mixer (10) according to claim 1, characterized in that a heating device is provided, by means of which the inner wall (26) can be heated at least in a respective subarea (64) in order to vaporize the second fluid (38).

6. Chamber mixer (10) according to claim 1, characterized in that the fluid introduction device (34) is designed for injecting a, in particular aqueous, urea solution.

7. Chamber mixer (10) according to claim 1, characterized in that beading (52) is incorporated on the inner wall (26), said beading being oriented with respect to the through-flow direction (22) in such a way that mixing of the first fluid (58) with the second fluid (38) is favored.

8. Chamber mixer (10) according to claim 1, characterized in that the one chamber contour of the inner chamber (28) tapers downstream in order to favor the mixing of the first fluid (58) with the second fluid (38).

9. Chamber mixer (10) according to claim 1, characterized in that the inlet opening (18) and the outlet opening (20) are arranged on a first housing side (16).

Description

[0027] The drawings show:

[0028] FIG. 1 A schematic perspective view of a chamber mixer for an exhaust after-treatment system of a motor vehicle;

[0029] FIG. 2 A schematic top view of the chamber mixer according to FIG. 1;

[0030] FIG. 3 A sectional side view of the chamber mixer according to the previous figures;

[0031] FIG. 4 A sectional front view of the chamber mixer according to the previous figures;

[0032] FIG. 5 A schematic side view of the chamber mixer according to the previous figures;

[0033] FIG. 6 A sectional top view of the chamber mixer according to the previous figures;

[0034] FIG. 7 A further sectional side view of another embodiment of the chamber mixer;

[0035] FIG. 8 A schematic top view of an inner wall as well as a double swirl plate of the chamber mixer according to FIG. 7; and

[0036] FIG. 9 A schematic sectional front view of the chamber mixer according to FIG. 7.

[0037] FIG. 1 shows a schematic perspective view of a chamber mixer 10 for an exhaust after-treatment system of a motor vehicle. The exhaust after-treatment system is used for exhaust after-treatment, in which combustion gases from an internal combustion engine of the motor vehicle are cleaned. In this way, emissions can be reduced during use of the motor vehicle, which may in particular be a passenger car or a truck.

[0038] In particular, the exhaust after-treatment system can be operated on the basis of selective catalytic reduction if the internal combustion engine is a diesel engine. The exhaust after-treatment can thus reduce nitrogen oxides, in particular nitrogen monoxide and nitrogen dioxide, from the exhaust gas, which can flow through the chamber mixer 10 as the first fluid 58, in at least one SCR catalytic converter. The exhaust after-treatment in the chamber mixer 10 is advantageously initiated by bringing a reductant, which is injected into the chamber mixer 10 as a second fluid 38, into contact with the exhaust gas, i.e., the first fluid 58. The mixture of first and second fluid flows from the chamber mixer 10 into the at least one SCR catalytic converter, whereupon a selective catalytic reaction known per se takes place in the SCR catalytic converter.

[0039] It has been shown in the prior art that a low mixing homogeneity between the fluids leads to poor exhaust gas after-treatment values or that chamber mixers are used in which the fluid can only flow with a high counterpressure. This favors deposit growth and thus deposits from the fluid in the previous chamber mixers.

[0040] These disadvantages of the prior art can be avoided by the chamber mixer 10 according to the invention as shown.

[0041] For this purpose, the chamber mixer 10 has an internal volume 14 delimited by a housing 12. As indicated by the first arrow P1 shown in FIG. 1, the first fluid 58 flows into the internal volume 14 through an inlet opening 18 arranged at one end of the internal volume 14 on a first housing side 16. Together with the mixed second fluid 38, the first fluid 58 flows to an outlet opening 20 arranged at the other end of the internal volume 14 on the (same) first housing side 16 along a through-flow direction 22 through the internal volume 14 and, as indicated by a second arrow P2, out of the outlet opening 20 from the internal volume 14 and thus out of the housing 12 of the chamber mixer 10.

[0042] In the chamber mixer 10, at least a second housing side 80 of the housing 58 is double-walled with an outer wall 24 and an inner wall 26 shown in FIGS. 3, 4, 6, 7 and 9, which divides the internal volume 14 into an inner chamber 28 and an outer chamber 30 located between the inner wall 26 and the outer wall 24, which can be seen, for example, in FIG. 3. The second housing side 80 of the housing 12 and is preferably designed opposite the inlet opening 18 and the outlet opening 20.

[0043] The chamber mixer 10 is further designed so that the first fluid 58the exhaust gas of the internal combustion engineflowing in through the inlet opening 18, in particular in gaseous form, can be divided, or is divided, in particular through the inlet opening 18, into a main flow 54 flowing through the inner chamber 28 and an auxiliary flow 56 flowing through the outer chamber 30. For this purpose, the inlet opening 18 has a first partial inlet opening 42 for the inner chamber 28 with its main flow 54 and a second partial inlet opening 62 for the outer chamber 30 with its auxiliary flow 56. Once the first fluid 58 has flowed into the housing 12 through the inlet opening 14 and the first and second partial inlet openings 60 and 62, the first fluid 58 is diverted into the main flow 54 and the auxiliary flow 56, respectively, in the through-flow direction 22. The outer chamber 30 initially runs along a third housing side which, starting from the inlet opening 18, forms an angle with the second housing side 80 and merges into it.

[0044] Furthermore, a flow device 32 is provided, by means of which the main flow 54 can be subjected to a double swirl 70, in particular a symmetrical double swirl, in the through-flow direction 22. This means that the first fluid 58, when flowing transversely to the through-flow direction 22 downstream through the inner chamber 28, is divided downstream of the first partial inlet opening 42 in the inner chamber 28 into a clockwise swirling first partial main flow 66 and a counterclockwise swirling second partial main flow 68 of the main flow 54. In each of the two partial main flows 66 and 68, the first fluid 58 or a fluid mixture of the first and second fluids 58 and 38 essentially moves in a spiral as it flows through the inner chamber 28.

[0045] Furthermore, a fluid introduction device 34 with an introduction end 36 is provided in the third housing side. The introduction end 36 is arranged in the outer chamber 30 and can therefore be flowed around by the auxiliary flow 56. A second fluid 38, in particular a liquid fluidthe reductant, such as urea solutioncan be injected into the inner chamber 28 through an introduction opening 40 in the inner wall 26 via the fluid introduction device 34. Furthermore, a merging device 42 is provided downstream in the through-flow direction 22, by means of which the main flow 54 with its two partial main flows 66 and 68 and the auxiliary flow 56 can be guided into one another and thus mixed with one another. The merging device 42 is essentially provided upstream of the outlet opening 20 in the internal volume 14. The mixed fluids 58 and 38 are deflected in the internal volume 14 in the area of the merging device 42 at a fourth housing wall 64 and then flow out of the outlet opening 20 of the housing 12 and thus out of the chamber mixer 10. The merging device 42 has at least one through-hole opening 48, through which the auxiliary flow 56 enters the inner chamber 28. The fourth housing wall 64 thereby extends from the second housing side 80 to the outlet opening 20.

[0046] FIG. 2 shows a schematic top view of the chamber mixer 10 according to FIG. 1 and serves in particular to illustrate the sections shown in FIGS. 3 and 4 along the line A1-A1 and the line A2-A2.

[0047] Thus, FIG. 3 shows the chamber mixer 10 according to the two preceding figures in a schematic sectional side view along the line A1-A1, whereby the two chambers formed from the internal volume 14, the inner chamber 28 and the outer chamber 30, are particularly advantageously recognizable here. According to FIG. 3, the through-flow direction 22 essentially extends along a longitudinal extension direction of the chamber mixer 10, whereby the respective fluid 58 and 38 can deviate from the longitudinal extension direction of the chamber mixer 10 in a respective transverse extension direction, in particular in the vicinity of the inlet opening 18 and the outlet opening 20. In the embodiment shown, the first fluid 58 is deflected downstream of the inlet opening 18 by an angle of approximately 90 in the through-flow direction 22 and the first fluid 58 and the second fluid 38 mixed with the first fluid 58 are also deflected upstream of the outlet opening 20 by an angle of 90 to the through-flow direction 22. It goes without saying that deflection angles are also possible. The first fluid 58 and second fluid 38 that are mixed together flow out of the outlet opening 20 from the chamber mixer 10 as a fluid mixture.

[0048] For example, the flow device 32 may include a double swirl plate 44 arranged in the first partial inlet opening 60 of the inlet opening 18. In a first embodiment according to FIGS. 1 to 6, the double swirl plate 44 has a plurality of lamellae 72 which are oriented in the longitudinal direction or through-flow direction 22 and are set to generate the clockwise swirl of the first partial main flow 66 and the counterclockwise swirl of the second partial main flow 68 correspondingly with respect to the first fluid 58 flowing towards the inlet opening 18. The first fluid 58 flows through openings 50 between the lamellae 72 into the chamber mixer 10, where it is deflected accordingly. The second partial inlet opening 62 is free of a flow device. Furthermore, as shown in a schematic, sectional frontal view of FIG. 4 along A2-A2, the flow device 32 can have at least one deflection element 46, which is arranged in the inner chamber 28 and/or on the inner wall 26. The deflection element 46 is used in particular to apply the double swirl 70 to the main flow 54 or to reinforce or maintain it and can also guide it downstream towards the outlet opening 20. The deflection element 46 has an essentially triangular cross-section, with one edge 78 of the deflection element 46 facing the inlet opening 18. The edge 78 of the deflection element 46 essentially begins in the central area of the inlet opening 18 and extends in the internal volume 14 to the outlet opening 20. The deflection element 46 is formed by a recess 76 in the second housing side 80, which leads to the essentially triangular cross-section of the inner wall 26 and projects into the internal volume 14. It can be seen in particular in FIGS. 3 and 4 that the outer wall 24 also has the triangular cross-section and thus the outer chamber 30 also has the triangular cross-section in the area of the edge 78.

[0049] FIG. 5 shows a schematic side view of the chamber mixer 10, with the sectional plane A3-A3 shown in FIG. 6 marked.

[0050] FIG. 6 shows a schematic top view of the chamber mixer 10. The angled lamellae 72 of the double swirl plate 44 are particularly clearly visible, as is a web 74 of the double swirl plate 44 arranged centrally between the lamellae 72. The web 74 ensures improved stability of the double swirl plate 44. There are also openings 50 between the web 74 and the lamellae 72 to the left and right of it. Furthermore, it can be seen that, in contrast to the first partial inlet opening 60 with its double swirl plate 44, the second partial inlet opening 62 has no flow device and the first fluid 58 can flow into the outer chamber 30 without being deflected. In particular, it can be seen from FIG. 6, as also from FIG. 2, that the internal volume 14 of the chamber mixer 10 has a decreasing cross-section along the through-flow direction 22 from the inlet opening 18 to the outlet opening 20. Overall, the housing 12 and thus the internal volume 14 tapers from the inlet opening 18 towards the outlet opening 20, so that a velocity of the first fluid 58 and the second fluid 38 increases in the internal volume 14 of the chamber mixer 10 from the inlet opening 18 towards the outlet opening 20, whereby an improved mixing of the first fluid 58 with the second fluid 38 can be achieved.

[0051] FIGS. 7 to 9 show a further embodiment of the chamber mixer 10, with FIG. 7 showing the chamber mixer 10 in a sectional view analogous to that of FIG. 3. Identical components or components with the same effect are marked with the same reference symbols as in the embodiment shown in FIGS. 1 to 6. FIG. 7 shows how the second fluid 38 can be introduced into the inner chamber 28 by the fluid introduction device 34 through the introduction opening 40 via the introduction end 36. In particular, the introduction can take place in liquid form so that the liquid second fluid 38 can come into contact with the inner wall 26. In order for the second fluid 38 to be advantageously used for the exhaust after-treatment, it should advantageously mix with the first fluid 58the exhaust gasin the gaseous phase in the double swirl 70. For this purpose, a heating device, not shown in more detail, can advantageously be provided, which heats the inner wall 26 at least in a subarea 64, in particular the area in which the second fluid 38 meets the inner wall 26, whereby the evaporation of the second fluid 38 and thus its transition from the liquid to the gaseous phase is at least favored.

[0052] FIG. 7 also shows beading 52 formed on the inner wall 26. The beading 52 is oriented essentially transverse to the through-flow direction 22 such that mixing of the first fluid 58 with the second fluid 38 is favored, since, for example, in addition to the double swirl 70, turbulence can be formed at the beading 52 in the inner chamber 34 in the fluid or in the mixture of the first and second fluids 58 and 38.

[0053] The fluid introduction device 34 is advantageously designed so that a second fluid 38, in particular an aqueous urea solution, can be injected. The urea solution can be converted to ammonia in a chemical reaction in the chamber mixer 10, so that the ammonia can advantageously bind or neutralize the nitrogen oxides in the exhaust gas in an SCR catalytic converter downstream of the chamber mixer 10. Furthermore, the merging device 42 has a plurality of through-hole openings 48 such that the first fluid 58 can enter the inner chamber 34 from the outer chamber 30 through the through-hole openings 48 and mix with the first and second fluids 58 and 38 in the inner chamber 34, thereby allowing further enhanced mixing of the first and second fluids 58 and 38.

[0054] FIG. 8 shows a schematic top view of the double swirl plate 44 in a second embodiment according to FIGS. 7 to 9 in the first partial inlet opening 60 of the inlet opening 18, which is arranged above the inner wall 26 provided with the through-hole openings 48 in the viewing direction of the figure. A single opening 50 can thereby be seen here in particular, which tapers in the downstream direction of the through-flow direction 22 towards the outlet opening 20 and is arranged symmetrically transversely thereto in an alternative flow device.

[0055] FIG. 9 shows the section A4-A4, the position of which at the chamber mixer 10 is shown in FIG. 7, with the arrows indicating the first partial main flow 66 and the second partial main flow 68 of the double swirl 70 of the first fluid 58 and the fluid mixture respectively. In order to advantageously maintain or increase the double swirl 70 or to favor a mixture of the first fluid 58 and the second fluid 38, a cross-section of the inner chamber 28 can become smaller, especially downstream. At least the inner chamber 28, for example, can thereby taper downstream.

[0056] The first partial main flow 66 and the second partial main flow 68 of the double swirl 70 of the first fluid 58 or of the fluid mixture are generated by lamellae 72 in the opening 50 of the double swirl plate 44, which are bent inwards in the direction of the inner chamber 28, and also by the inner wall 26, which has a concave shape, at least at its edges. As shown in section A4-A4, the two lamellae 72 of the opening 50 do not extend as far into the inner chamber 34 as in the direction of the outlet opening 20 of the chamber mixer 10, as can be seen in FIG. 7.

[0057] Through the chamber mixer 10 shown in the figures, it is possible to contribute in a particularly advantageous way to exhaust after-treatment by means of the exhaust after-treatment system.

[0058] This results in several advantages. For example, the chamber mixer 10 can be designed to be particularly compact, so that the installation volume is particularly small. Furthermore, additional openings and/or holes can be dispensed with as an obstruction point, which can reduce deposition growth of, for example, the urea solution on the surfaces of the housing 12 in contact with the inner chamber 28 and the outer chamber 30. In addition, the overall sturdiness of the chamber mixer 10 can be increased, for example, by dispensing with an extra mixing device in the internal volume 14. Furthermore, the internal volume can essentially be formed without edges and/or obstructions, which enables a particularly low counterpressure when flowing through in the through-flow direction 22. Thus, the chamber mixer 10 shown here results in a particularly advantageous exhaust after-treatment.

LIST OF REFERENCE SIGNS

[0059] 10 Chamber mixer [0060] 12 Housing [0061] 14 Internal volume [0062] 16 Housing side [0063] 18 Inlet opening [0064] 20 Outlet opening [0065] 22 Through-flow direction [0066] 24 Outer wall [0067] 26 Inner wall [0068] 28 Inner chamber [0069] 30 Outer chamber [0070] 32 Flow device [0071] 34 Fluid introduction device [0072] 36 Introduction end [0073] 38 Second fluid [0074] 40 Introduction opening [0075] 42 Merging device [0076] 44 Double swirl plate [0077] 46 Deflection element [0078] 48 Through-hole opening [0079] 50 Opening [0080] 52 Beading [0081] 54 Main flow [0082] 56 Auxiliary flow [0083] 58 First fluid [0084] 60 First partial inlet opening [0085] 62 Second partial inlet opening [0086] 64 Subarea [0087] 66 First partial main flow [0088] 68 Second partial main flow [0089] 70 Double swirl [0090] 72 Lamella [0091] 74 Web [0092] 76 Recess [0093] 78 Edge [0094] 80 Second housing side [0095] P1 Arrow [0096] P2 Arrow