CN216617626U - Mixer for mixing exhaust gas and reducing agent, and exhaust line - Google Patents

Abstract

The utility model provides a mixer for mixing exhaust gas and reducing agent and an exhaust line, the mixer comprises a box body (2) and a reducing agent sprayer (3), wherein the inlet aperture (4) and the spray aperture (6) are arranged substantially aligned along a first axis (X) at two opposite ends of the cartridge (2), and the mixer (1) further comprising a first inner wall (7) located at the cartridge body (2) and a duct (8) comprising an elbow (12), the first inner wall (7) dividing the cartridge body (2) into a first chamber (10) comprising the inlet aperture (4) and the spray aperture (6) and a second chamber (11) comprising the at least one outlet aperture (5), and, the pipe (8) is arranged in the first chamber (10) such that its first end penetrates the first inner wall (7) in a sealed manner at the inner hole (9) and its second free end faces the spray hole (6).

Description

Mixer for mixing exhaust gas and reducing agent, and exhaust line

Technical Field

The utility model relates to a mixer for reducing agents in exhaust gases. Such a mixer is usually arranged in the exhaust line of an internal combustion engine. Its function is to mix a reducing fluid (usually aqueous ammonia or urea solution: AUS 32, DEF) with the exhaust gases in preparation for the treatment of the mixture by at least one selective catalytic reducing agent (english: "selective catalytic reduction" or SCR) to reduce the nitrogen oxides.

Background

To implement such a mixer, different architectures are known. According to a possible embodiment, the mixer comprises a cartridge and a nebulizer. The cartridge is sealed closed except for the inlet orifice, the outlet orifice and the spray orifice. The exhaust gas flows through the cartridge body from the inlet aperture to the outlet aperture. A sprayer is disposed in the outer wall of the cartridge body to spray the reducing agent through the spray holes into the exhaust gas flow.

It is also known, in order to optimize the reducing agent/exhaust gas mixture, to spray the reducing agent in as long a gas stream as possible in order to increase the common flow-through time of the two components and thus to improve the mixing. To this end, although the space available in the engine and/or the exhaust compartment is generally limited, it is still known to use an inner wall forming a deflector, arranged in the box and able to deflect the flow of exhaust gases, in order to create as long a flow path as possible in the restricted volume allocated to the mixer.

The present invention solves the problem of implementing a mixer by adding the following limitations: an inlet aperture and a spray aperture are provided at opposite ends of the cartridge body substantially in axial alignment.

SUMMERY OF THE UTILITY MODEL

To accommodate this limitation, the utility model uses a deflector of the gas, of the exhaust gas or of the mixture of exhaust gas and reducing agent, consisting of an inner wall that divides the box into two compartments and a duct comprising an elbow.

The utility model relates to a mixer for mixing an exhaust gas and a reducing agent, comprising a cartridge which is hermetically closed except for an inlet opening, at least one outlet opening and a spray opening, which opening extends from the inlet opening up to the at least one outlet opening in the exhaust gas cartridge, and a reducing agent sprayer which is arranged in an outer wall of the cartridge for spraying the reducing agent into the exhaust gas flow through the spray opening, wherein the inlet opening and the spray opening are arranged at two opposite ends of the cartridge substantially aligned along a first axis, and in that the mixer further comprises a first inner wall inside the cartridge and a duct comprising an elbow, which first inner wall, except for the at least one inner opening, divides the cartridge in a sealed manner in a first direction substantially parallel to the first axis into a first chamber comprising the inlet opening and the spray opening and a second chamber comprising the at least one outlet opening, and the conduit is arranged in the first chamber with its first end portion passing in a sealed manner through the first inner wall at the inner bore substantially along a second axis perpendicular to the first axis and with its second free end facing the spray aperture.

Specific features or embodiments that may be used alone or in combination are as follows:

the elbow is placed facing the inlet aperture,

-the conduit has a straight portion between the bend and the second end substantially along the first axis,

-the inner bore is arranged as far away as possible from the spray bore along the first axis, such that the straight portion is as long as possible,

the angle of the elbow is between 60 ° and 120 °, preferably between 60 ° and 95 °, more preferably between 80 ° and 90 ° and even more preferably equal to 90 °,

the distance of the second end from the spray orifice is a fraction of the size of the duct 8, at least equal to 0.5, preferably at least equal to 0.75 and more preferably equal to 1,

the second end comprises a vortex device comprising longitudinal cuts equipped with fins distributed evenly in angle,

-the at least one outlet aperture is arranged substantially along a third axis perpendicular to the first and second axes,

the first inner wall is L-shaped and comprises a first planar blank substantially parallel to the XZ plane and a second planar blank substantially parallel to the XY plane, the first blank accommodating the inner hole,

the first inner wall also comprises at least one bypass bore of the duct between the first and second chambers, preferably provided in the first blank and also preferably in the vicinity of the inner aperture, the total cross section of said at least one bypass bore preferably being less than 30% and more preferably less than 20% of the cross section of the duct,

the mixer further comprises a second inner wall comprising a first sub-chamber dividing the second chamber in a direction substantially parallel to the first axis into a first sub-chamber comprising the first end of the duct and a second sub-chamber comprising the at least one outlet aperture, the second inner wall comprising substantially central diffuser apertures or substantially surface evenly distributed perforations.

According to a second aspect, the utility model relates to an exhaust line comprising such a mixer.

Drawings

The utility model will be better understood from reading the following description, purely by way of example, with reference to the accompanying drawings, in which:

figure 1 shows a perspective view of an embodiment of a mixer according to the utility model,

fig. 2 shows a perspective view of the embodiment of fig. 1, with the cassette open,

figure 3 shows a top view of the mixer of figure 2,

figure 4 shows a top view of a variant with a conical swirling device,

figure 5 shows a top view of a variant in which the angle of the elbow is 70 °.

List of reference numerals

1: mixer, 2: a box body, 3: atomizer, 4: inlet hole, 5: outlet orifice, 6: spray orifice, 7: first inner wall, 8: a pipeline 9: internal bore, 10: first chamber, 11: second chamber, 12: elbow pipe, 13: vortex device, 14: incision, 16: straight line portion, C: gas circulation, D: reverse turn, R: a straight line portion.

Detailed Description

Referring to fig. 1, a mixer 1 for mixing an exhaust gas and a reducing agent includes a cartridge body 2 and a reducing agent sprayer 3 (not shown), but is shown by arrows indicating an axis and a spraying direction thereof. According to a possible embodiment, the box 2 may be substantially parallelepiped as shown. In addition to three wells: an inlet opening 4, at least one (here two) outlet opening 5 and a spray opening 6, the cartridge body 2 being hermetically closed. The holes are connected such that the exhaust gas circulates in the box 2 from the inlet hole 4 up to the at least one outlet hole 5. A sprayer 3 is provided in the outer wall of the case 2 to spray the reducing agent through spray holes 6 in the exhaust gas flow.

As can be seen more particularly in fig. 2, the exhaust gas flow is illustrated by arrows C.

Here, the reducing agent spray takes place in a substantially straight branch R of the flow-through C, which branch R follows the return D.

It is an object of the present invention to provide a mixer 1 such that the inlet orifice 4 and the spray orifice 6 are arranged at two opposite ends of the cartridge 2, substantially aligned along the first axis X.

Referring to fig. 2, the mixer 1 further comprises a first inner wall 7 at the box 2 and a tube 8 comprising an elbow 12. The first inner wall 7, apart from the at least one inner hole 9, divides the box 2 in a sealed manner into a first chamber 10 and a second chamber 11 along a direction substantially parallel to the first axis X. The first inner wall 7 is also connected to the inner surface of the outer wall of the box 2 on all its end edges. The first chamber 10 has an inlet aperture 4 and a spray aperture 6. The second chamber 11 has one or more outlet openings 5.

The conduit 8 is arranged in the first chamber 10. The first end of the duct passes in a sealed manner through the first inner wall 7 at the inner hole 9, in an orientation substantially along a second axis Y perpendicular to the first axis X. There may be an angular offset of +/-30 deg. from the perpendicular preferred for orientation. The conduit 8 is held in place in the inner bore 9 by fixing means fixed to the first inner wall 7. The second end is free in that it is not connected to the wall. Alternatively, according to an embodiment not shown, the second end may be connected to the wall in the vicinity of the spray orifice 6 in a non-sealing manner to strengthen the assembly. The second end is arranged to face the spray aperture 6. The first end is downstream and the second end is upstream with respect to the gas communication portion C.

The duct 8, by its shape and arrangement, forces the exhaust gases coming from the inlet hole 4 to undergo a return D in order to enter the duct 8 through the second end, continuing its flow C. The arrangement of the spray aperture 6 facing the second end and the sprayer 3 with its axis aligned with the first axis X allows spraying in the duct 8 and the flow C even if this flow C enters the duct 8.

The duct 8 may have any shape in cross-section. The conduit 8 preferably has a circular cross-section as shown, due to the lowest cost. Alternatively, the oval or elliptical cross-section may be retained to increase the gas passage cross-section to reduce overall back pressure without increasing the height of the cartridge 2.

According to another feature, the elbow 12 is arranged facing the inlet aperture 4. The elbow 12 thus receives the exhaust gas heat flow entering the box 2 from the outside of the pipe 8, which is arranged through the box 2. This results in heating of the elbow 12, whether for the outer wall or the inner wall of the elbow 12.

This heating is advantageous because it is expected that a portion of the reducing agent sprayed by the sprayer 3 into the conduit 8 lying substantially on a straight line parallel to the first axis X may affect an outer bend of the inner surface of the elbow 12. The heating maximizes the ability of the reductant and its contained water to evaporate in the elbow 12. This allows to reduce the formation of a liquid film on this area. This allows reducing the risk of solid deposition of which the liquid film is a precursor.

According to another feature, the duct 8 has, between the second end and the bend 12, a rectilinear portion 16 substantially along the first axis X. Such a straight portion 16 guides the gas in the straight portion R of trajectory C and is advantageously aligned with the jet of reducing agent sprayed by the sprayer 3. The gas is guided by the duct 8 along a rectilinear flow R which is therefore parallel to the sprayed reducing agent, so as to promote mixing between the exhaust gas and the reducing agent. The fact that the portion 16 is rectilinear also advantageously delays the meeting of the wall with the gas flow, which flow risks depositing the reducing agent on the wall.

According to another feature, the inner hole 9 is arranged as far as possible from the spray hole 6. The distance is here measured along the first axis X. This is equivalent to arranging the inner bore 9 as close as possible to the inlet bore 4. This allows to obtain a construction that makes the rectilinear portions 16 as long as possible for a given size of the box 2, which is generally limited by the integration possibilities. This allows to maximize the possibility of delaying the encounter of the gas flow (here the mixture of exhaust gas and reducing agent) with the wall and thus delaying the deposition of the reducing agent on the wall.

As shown in fig. 2-4, from the respective orientations, it can be seen that elbow 12 has an angle substantially equal to 90 °. The portion 16 integral with the second end is substantially parallel to the first axis X, while the portion integral with the first end is substantially parallel to the second axis Y. According to another feature, the elbow 12 has an angle comprised between 60 ° and 120 °, preferably between 60 ° and 95 °, more preferably between 80 ° and 90 ° and more preferably equal to 90 °. Fig. 5 shows an arrangement with an angle of 120.

In order to allow the return D of the exhaust gas from the inlet aperture 4 when flowing from the first chamber 10 to the conduit 8, it is appropriate that there is a minimum distance between the second end of the conduit 8 and the spray aperture 6 and the wall carrying it. This distance may be expressed as a proportion of the size of the duct 8. This dimension is understood here to mean a transverse dimension, for example a diameter in the case of a cylindrical pipe. According to another feature, the ratio is at least equal to 0.5, preferably at least equal to 0.75 and more preferably equal to 1.

In order to facilitate the achievement of the fold back D and to produce a flow around the sprayed droplets that is as uniform as possible and to facilitate the mixing of the gas and the reducing agent by causing an acceleration of the gas flow when passing the second end, according to another feature, the second end comprises a vortex device 13. Such a vortex device 13 is capable of inducing a clockwise or counter-clockwise vortex of the airflow entering the duct 8. It generally comprises longitudinal cuts 14 equipped with fins evenly distributed angularly around the second end. The vortex device 13 may be cylindrical as shown in fig. 2 and 3. Such a vortex device 13 may also comprise a conical cap, as shown in fig. 4 and 5. The longitudinal cut provided with fins may be implemented in the substantially cylindrical portion of the end portion and/or in the conical portion extending therefrom.

Another way to reduce the pressure loss caused by the fold back D at the entrance of the duct 8 is to provide a much larger volume upstream with respect to the volume of the duct 8. Furthermore, according to another characteristic, the volume of the first chamber 10 is greater than the volume of the duct 8, preferably in a ratio at least equal to 2, and still preferably at least equal to 4.

According to another feature, said at least one outlet aperture 5 is arranged substantially along a third axis Z perpendicular to the first axis X and to the second axis Y. The outlet opening 5 of the mixer 1 generally provides access to a selective catalytic reducer (english: "selective catalytic reduction" or SCR). The mixer 1 shown in fig. 1 shows two outlet openings 5 and supplies two SCRs.

According to another feature, the first inner wall 7 has an L-shape. According to this feature, the first inner wall 7 comprises a first planar blank substantially parallel to the XZ plane, i.e. the plane containing the first axis X and the third axis Z, and a second planar blank substantially parallel to the XY plane, i.e. the plane containing the first axis X and the second axis Y. As shown in fig. 1, the first vertical blank accommodates the internal aperture 9 and the second blank is horizontal.

According to another feature, which allows reducing pressure losses, the first inner wall 7 also comprises at least one bypass drilling (not shown) of the duct 8, between the first chamber 10 and the second chamber 11, which is preferably provided in the first blank, and still more preferably in the vicinity of the inner hole 9, if present. The gas passing through such a bypass bore is the exhaust gas that is not mixed with the reductant. Furthermore, it is appropriate to limit the total cross section of the at least one bypass borehole, i.e. the cumulative cross section of all boreholes. A value of at most 30% of the cross-section of the duct 8 is satisfactory, a value of at most 20% being preferred.

According to another feature, the connection of the first blank with the second blank, i.e. substantially along the first axis X, advantageously has a minimum radius. The radius is at least equal to 2mm, preferably at least equal to 5mm, more preferably at least equal to 20 mm. Such a radius facilitates the material realization thereof by forming the plate. Furthermore, the radius facilitates the flow of gas.

According to another feature, the mixer 1 further comprises a second internal wall (not shown). Which divides the second chamber 11 in a direction substantially parallel to the first axis X into a first sub-chamber comprising the first end of the duct 8 and a second sub-chamber comprising the at least one outlet opening 5. The second inner wall comprises a diffuser hole or substantially evenly distributed perforations in its center. Thus, the conduit 8 discharges the gas, here a mixture of exhaust gas and reductant, into the first sub-chamber via the internal aperture 9. The gas then passes from the first sub-chamber to the second sub-chamber to reach the one or more outlet holes 5. This is achieved by a single diffuser aperture provided substantially in the centre of the second inner wall. This arrangement advantageously makes it possible to distribute the gas between the two outlet orifices 5 and the SCR downstream thereof. Alternatively, the perforations evenly distributed over the surface of the second inner wall ensure the equivalent function of a balanced distribution between the different outlets 5.

Another object of the utility model is an exhaust line comprising such a mixer 1.

The utility model has been illustrated and described in detail in the drawings and foregoing description. This should be regarded as illustrative and given by way of example, and not as limiting the utility model to this description. Many alternative embodiments are possible.

Claims (12)

1. Mixer (1) for mixing an exhaust gas and a reducing agent, comprising a cartridge (2) and a reducing agent sprayer (3), the cartridge (2) being hermetically closed except for an inlet opening (4), at least one outlet opening (5) and a spray opening (6), the exhaust gas circulating in the cartridge (2) along an exhaust gas throughput (C) extending from the inlet opening (4) up to the at least one outlet opening (5), the sprayer (3) being arranged in an outer wall of the cartridge (2) for spraying the reducing agent into the exhaust gas throughput (C) through the spray opening (6),

characterized in that said inlet hole (4) and said spraying hole (6) are arranged substantially aligned along a first axis (X) at two opposite ends of said cartridge (2), and in that said mixer (1) further comprises a first inner wall (7) located at said cartridge (2) and a duct (8) comprising an elbow (12), said first inner wall (7) dividing said cartridge (2) in a sealed manner, in a direction substantially parallel to said first axis (X), except for at least one inner hole (9), into a first chamber (10) comprising said inlet hole (4) and said spraying hole (6) and a second chamber (11) comprising said at least one outlet hole (5), and in that said duct (8) is arranged in said first chamber (10) so that a first end of said duct passes in a sealed manner through said first chamber at said inner hole (9) along a second axis (Y) perpendicular to said first axis (X), and in that said duct (8) is arranged in said first chamber (10) so that a first end of said duct passes in a sealed manner along a second axis (Y) at right angle to said first axis (X) at said inner hole (9) The inner wall (7) and its second free end face the spray aperture (6).

2. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that said elbow (12) is arranged facing said inlet aperture (4).

3. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that said duct (8) has a rectilinear portion (16) substantially along said first axis (X) between said elbow (12) and the second end.

4. Mixer (1) for mixing exhaust gases and reducing agent according to claim 3, characterized in that the inner aperture (9) is arranged as far away as possible from the spray aperture (6) along the first axis (X), so that the straight section (16) is as long as possible.

5. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that the elbow (12) has an angle between 60 ° and 120 °.

6. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that the distance of the second end from the spray orifice (6) is at least a fraction of the size of the duct (8) equal to 0.5.

7. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that the second end comprises a swirling device (13) comprising longitudinal slits (14) equipped with fins distributed evenly at an angle.

8. Mixer (1) for mixing exhaust gases and a reducing agent according to claim 1, characterized in that said at least one outlet opening (5) is arranged substantially along a third axis (Z) perpendicular to said first axis (X) and said second axis (Y).

9. Mixer (1) for mixing an exhaust gas and a reducing agent according to claim 1, characterized in that said first inner wall (7) is L-shaped, comprising a first planar blank substantially parallel to the XZ-plane and a second planar blank substantially parallel to the XY-plane, said first planar blank accommodating said inner hole (9).

10. The mixer (1) for mixing an exhaust gas and a reducing agent according to claim 9, characterized in that said first inner wall (7) further comprises at least one bypass drilling of said duct (8) arranged in said first planar blank between said first chamber (10) and said second chamber (11) and close to said inner hole (9), said at least one bypass drilling having a total section smaller than 30% of the section of said duct (8).

11. Mixer (1) for mixing exhaust gases and reducing agent according to claim 1, characterized in that it further comprises a second inner wall dividing said second chamber (11) along a direction parallel to said first axis (X) into a first sub-chamber comprising said first end of said duct (8) and a second sub-chamber comprising said at least one outlet orifice (5), said second inner wall comprising a diffuser hole or a substantially surface-evenly distributed perforation substantially centrally arranged.

12. An exhaust line, characterized in that it comprises a mixer for mixing an exhaust gas and a reducing agent according to any one of claims 1-11.

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