Automotive exhaust aftertreatment system having a swirl-back mixer

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 into an exhaust stream moving through the exhaust aftertreatment system 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
• 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,
• wherein the flow-back unit includes a flow-back baffle shaped to receive the mixture, 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, and
• 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 the doser axis, and a second lateral duct positioned adjacent the swirl unit on a second lateral side of the mixer body and the doser axis opposite the first lateral side.

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 such that the mixture travels circumferentially about the primary axis and toward the swirl unit and to make a second 180 degree turn such that the mixture travels away from the swirl unit and perpendicularly to the primary axis.