Patent Application
20200269189
The present disclosure relates to exhaust aftertreatment systems for automotive applications, and particularly to a reducing agent mixer for injecting and mixing a reducing agent into the exhaust stream.
A vehicle, in accordance with the present disclosure, includes a combustion engine and an exhaust aftertreatment system. The engine produces exhaust stream during operation and is coupled to the aftertreatment system via an exhaust passageway. The aftertreatment system is configured to inject a reducing agent, such as diesel emission fluid, into the exhaust stream. The reducing agent combines with the exhaust stream to cause a chemical reaction and reduce effluents, such as nitrous oxides (NOx), in the exhaust stream before it is released into the atmosphere.
In illustrative embodiments, the aftertreatment system includes a reducing agent mixer that is configured to improve mixing of the reducing agent into the exhaust stream, increase effluent removal efficiencies, and decrease reducing agent deposits on various components in the aftertreatment system. The reducing agent mixer includes a mixer body, a doser, and a reducing agent mixer sub-assembly. The mixer body defines a mixing chamber. The doser is configured to inject the reducing agent into the mixing chamber. The reducing agent mixer sub-assembly is located in the mixing chamber and is configured to induce mixing of the reducing agent and the exhaust stream.
The reducing agent mixer sub-assembly includes a swirl unit and a flow-back unit. The swirl unit defines a swirl chamber that induces a vortex of the exhaust stream directly adjacent to an injection point of the reducing agent. In illustrated embodiments, the swirl unit is configured to receive at least 50% of the exhaust stream moving through the reducing agent mixer. A mixture of the exhaust stream and the reducing agent is discharged from the swirl chamber toward the flow-back unit. The flow-back unit is configured to delay exit of the reducing agent from the mixer, to enhance mixing, and to increase the transformation rate of the reducing agent.
The flow back unit is configured to cause the mixture of the exhaust stream and the reducing agent discharged from the swirl chamber to turn 180 degrees twice before exiting the mixer. These turns increase the distance the mixture must travel before exiting the mixer to increase mixing. The flow back unit illustratively includes a flow-back baffle, a first lateral duct positioned on a first lateral side of the mixer body, and a second lateral duct positioned on a second lateral side of the mixer body. The flow-back baffle is shaped to cause the mixture to split into two halves and cause each half to make a 180 degree turn in opposite directions from one another. The first and second lateral ducts are positioned to receive a respective half of the mixture and are shaped to cause each half to make another 180 degree turn.
Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived.
The detailed description particularly refers to the accompanying figures in which:
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
An illustrative diesel engine vehicle 10 configured for over the road transportation is shown in
In the illustrative embodiment, the reducing agent mixer 16 includes a mixer body 24, a doser 26, and a reducing agent delivery sub-assembly 28 as shown in
The mixer body 24 includes a mixer can 34, an upstream baffle 36, and an optional downstream baffle 38 as shown in
The reducing agent delivery sub-assembly 28 includes a swirl unit 44 and a flow-back unit 46 positioned in the mixing chamber 42 as shown in
In use, at least 50% of the exhaust stream enters the primary exhaust stream inlet 32 and is guided by the swirl unit 44 to the injection point of the reducing agent as shown in
An exhaust stream/reducing agent mixture is discharged from the swirl chamber 48 and into an upstream flow-back chamber 66 defined at least in part by the flow-back unit 46 as shown in
In particular, the flow-back unit 46 is configured to split and redirect the mixture to cause the mixture to make a 180 degree turn such that the mixture travels upwardly back toward the swirl unit 44 as shown in
The swirl unit 44 includes a top wall 52, a first arcuate swirl fin 54, and a second arcuate swirl fin 56 as shown in
The first swirl fin 54 includes a head end 80 and a tail end 82 arranged downstream of the head end 80 relative to the primary axis 30 as shown in
The second swirl fin 56 defines a radial boundary of the swirl chamber 48 and includes a fin arm 86 and a fin body 88 as shown in
The first swirl passageway 81 terminates upstream of the second swirl passageway 83 as shown in
The flow-back unit 46 includes a flow-back baffle 68, a first lateral duct 70, and a second lateral duct 72 as shown in
The flow-back baffle 68 includes a panel 74 and an end wall 76 coupled to the panel 74 as shown in
The end wall 76 is shaped to receive the mixture of the exhaust stream and the reducing agent from the swirl unit 44 and is configured to split and redirect the mixture toward the first and second lateral ducts 70, 72 as shown in
The end wall 76 is spaced apart radially inward from the mixer can 34 to provide a bypass gap 90 between the mixer can 34 and an outer surface 92 of the end wall 76 as shown in
In the illustrative embodiment, the panel 74 is contoured and includes a basin 96, a first plateau 98 and a second plateau 100 as shown in
In the illustrative embodiment, the first and second lateral ducts 70, 72 are mirror images of one another and are each shaped to define a lateral duct passageway 102, 104, respectively, as shown in
The downstream flow-back chamber 67 is defined between the panel 74 of the flow-back unit 46 and the downstream baffle 38 as shown in
The downstream baffle 38 is shaped to enhance mixing and increase a transformation rate of the reducing agent prior the mixture being sent to the SCR 18. The downstream baffle 38 includes a ring 110, a radially outer rim 112, and a radially inner rim 114 as shown in
The ring 110 is formed to include a plurality of outlet holes 116 in at least a portion of the ring 110 as shown in
In illustrative embodiments, the entire diameter of the mixer 16 may be used to delay impingement therefore reducing liquid film on parts of the mixer 16. The mixer may be configured to send flow through lateral ducts 70, 72 to enhance mixing and increase DEF transformation rate to NH3. The mixer 16 may be configured to reduce backpressure in the aftertreatment system. The mixer may be configured to generate a swirling around the doser tip using more than 80% of exhaust flow across the mixer diameter and send back the mixture to each side of the mixer through the horse shoe ducts.
In illustrative embodiments, at least 50% of exhaust flow enters the main inlet opening 32. The exhaust flow may be collected in a manifold 44 and distributed through split openings 81, 83. The exhaust flow going through the split openings 81, 83 may generate a swirl around the doser injection point. The swirl center coincides to the doser axis 31. The exhaust flow and reducing agent may be mixed in the direction of the doser axis 31. The mixture may follow a long transformation path which is the diameter of the mixer and a small amount of the original spray may hit the opposite wall 76. Once the mixture reaches the opposite wall 76 the exhaust flow splits and is directed to enter in lateral ducts 70, 72 on each side of the mixer 16. The exhaust flow may be submitted to a 180 degree direction change in each lateral duct enhancing mixing and DEF transformation to NH3. The mixture may then be distributed to the inlet face of the SCR.
The following numbered clauses include embodiments that are contemplated and non-limiting:
Clause 1. An exhaust aftertreatment system for use with a diesel engine, the system comprising
a mixer body defining an engine exhaust gas passageway that extends along a primary axis,
a doser configured to discharge reducing agent (DEF) into the engine exhaust gas passageway along a doser axis perpendicular to the primary axis, and
a reducing agent delivery sub-assembly, the sub-assembly including,
a swirl unit arranged along a doser axis perpendicular to the primary axis of the mixer body, the swirl unit defining a swirl chamber configured receive the reducing agent from the doser and to induce rotation of exhaust gas to encourage mixing with the reducing agent and discharge a mixture of the exhaust stream and the reducing agent from the swirl chamber along the doser axis, the mixture of the exhaust stream and the reducing agent comprising the exhaust gas and the reducing agent, and
a flow-back unit positioned downstream of the swirl unit and shaped to cause the mixture of the exhaust stream and the reducing agent discharged from the swirl chamber to make a first 180 degree turn in a first direction and to make a second 180 degree turn in a second direction.
Clause 2. The system or vehicle any other suitable clause or combination of clauses, wherein the swirl unit is formed to include a primary exhaust stream passageway that is configured to direct at least 50% of exhaust stream into the swirl chamber.
Clause 3. The system or vehicle any other suitable clause or combination of clauses, wherein the swirl unit includes a first arcuate swirl fin arranged in the swirl chamber around the doser axis, and a second arcuate swirl fin arranged in the swirl chamber around the doser axis, the second arcuate swirl fin offset from the first arcuate swirl fin along the primary axis to create split openings between the first arcuate swirl fin and the second arcuate swirl fin sized to induce rotation of exhaust gas entering the swirl chamber.
Clause 4. The system or vehicle any other suitable clause or combination of clauses, wherein the flow-back unit includes a flow-back baffle shaped to receive the flow of mixture solution, the flow-back baffle including a panel arranged generally perpendicular to the primary axis and an end wall arranged to extend upstream from the panel and shaped to cause the mixture discharged from the swirl chamber to make the first 180 degree turn.
Clause 5. The system or vehicle any other suitable clause or combination of clauses, wherein the flow-back unit further includes a first lateral duct positioned adjacent the swirl unit on a first lateral side of the mixer body, and a second lateral duct positioned adjacent the swirl unit on a second lateral side of the mixer body opposite the first lateral side.
Clause 6. The system or vehicle any other suitable clause or combination of clauses, wherein the first and second lateral ducts are configured to direct the mixture of the exhaust stream and the reducing agent from an upstream side of the panel to a downstream side of the panel.
Clause 7. The system or vehicle any other suitable clause or combination of clauses, wherein the first lateral duct is configured to receive a first half of the mixture of the exhaust stream and the reducing agent and the second lateral duct is configured to receive a second half of the mixture of the exhaust stream and the reducing agent, and the first and second lateral ducts are shaped to cause the first and second halves of the mixture to make the second 180 degree turn.
Clause 8. The system or vehicle any other suitable clause or combination of clauses, wherein the mixer body is spaced apart from the primary axis a first radial distance and the end wall of the flow-back baffle is spaced apart from the primary axis a second radial distance that is less than the first radial distance to define a bypass gap between the end wall of the flow-back baffle and the mixer body.
Clause 9. The system or vehicle any other suitable clause or combination of clauses, wherein the sub-assembly further includes an upstream baffle formed to include a primary inlet aperture that is aligned with the swirl unit and a plurality of bypass apertures arranged opposite the primary inlet aperture and radially offset from the flow-back baffle.
Clause 10. The system or vehicle any other suitable clause or combination of clauses, the subassembly further including a downstream baffle arranged perpendicular with the primary axis, the downstream baffle formed to include a central outlet defined by an inner rim and a plurality of secondary outlet holes formed in at least a portion of the downstream baffle.
Clause 11. A vehicle configured for over the road transportation, the vehicle comprising
a combustion engine, and
an automotive exhaust aftertreatment system coupled to the combustion engine to receive an exhaust stream from the combustion engine, the automotive exhaust aftertreatment system including a mixer body defining an engine exhaust gas passageway that extends along a primary axis, a doser configured to discharge reducing agent (DEF) into the engine exhaust gas passageway along a doser axis perpendicular to the primary axis, and a reducing agent delivery sub-assembly,
wherein the reducing agent sub-assembly includes a swirl unit arranged along a doser axis perpendicular to the primary axis of the mixer body and a flow-back unit positioned downstream of the swirl unit,
wherein the swirl unit defines a swirl chamber configured receive the reducing agent from the doser and to induce rotation into the exhaust stream to encourage mixing with the reducing agent and discharge a mixture of the exhaust stream and the reducing agent from the swirl chamber along the doser axis, and
wherein the flow-back unit is shaped to cause the mixture of the exhaust stream and the reducing agent discharged from the swirl chamber to make a first 180 degree turn in a first direction and to make a second 180 degree turn in a second direction.
While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
