Patent Application
20080216470
The invention relates to aftertreatment systems for internal combustion engine exhaust, and more particularly to flow distribution.
To address engine emission concerns, new standards continue to be proposed for substantial reduction of various emissions, including NOx and particulate emissions. Increasingly stringent standards will require installation of aftertreatment devices in engine exhaust systems. Some of the aftertreatment technologies require certain chemical species to be injected into the exhaust system. For example, HC or fuel is injected in some active lean NOx systems for NOx reduction, or in active diesel particulate filters (DPF) for regeneration to take place (oxidizing the soot and cleaning the filter), and urea solution is injected in selective catalytic reduction (SCR) systems for NOx reduction. These injected chemical species need to be well mixed with exhaust gas and evenly distributed before reaching catalysts or filters for the systems to perform properly.
The present invention arose during continuing development efforts directed toward the above exhaust aftertreatment systems.
In the preferred embodiment, flow distributor 36 is a perforated member receiving exhaust flowing laterally along first leg 26, and discharging the exhaust axially along second leg 28 through perforations 40. Flow distributor 36 has an inlet end 42 receiving exhaust flowing laterally thereinto, and has a distal end 44 laterally distally oppositely spaced from inlet end 42. Flow distributor 36 has a cross-sectional flow area which decreases as exhaust flows from inlet end 42 toward distal end 44. Inlet end 42 of flow distributor 36 has a first cross-sectional area lying in a first plane which extends along an axial direction and along a transverse direction, the transverse direction extending into the page of
Exhaust conduit or housing 12 extends axially along the noted axis 32 and has an upstream inlet at 16 for receiving exhaust from engine 14, and has a downstream outlet at 48 for discharging exhaust. Inlet 16 is a side inlet receiving exhaust flowing laterally into housing 12 relative to axis 32. Aftertreatment element 18 in the housing passes exhaust axially therethrough then to outlet 48. Flow distributor 36 receives exhaust flowing laterally from inlet 16 and re-distributes the exhaust to flow axially to aftertreatment element 18 in an evenly distributed flow pattern 38. As noted, flow distributor 36 is preferably a conically shaped diffuser tube pointing downstream laterally away from the inlet, and preferably includes a perforated sidewall which conically convergingly tapers as it extends laterally away from the inlet.
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The system provides a method for optimizing exhaust flow distribution to an aftertreatment element such as 18 in a side inlet configuration by providing a conically shaped diffuser tube 36 pointing downstream laterally away from inlet 16 and providing the diffuser tube with a perforated sidewall 46 which conically convergingly tapers as it extends laterally away from inlet 16, the method further comprising optimizing even exhaust flow distribution by adjusting the cone angle of the conically shaped diffuser tube 36 to optimize and achieve even flow distribution of exhaust flowing axially along axial direction 32 to aftertreatment element 18.
The system further provides a method for optimizing exhaust flow distribution to an aftertreatment element such as 18 in a side inlet configuration by providing a diffuser tube 50, 62 extending downstream laterally away from inlet 16, providing the diffuser tube 50, 62 with a variable perforation pattern 52, 64 providing a diffuser outlet flow area which decreases as exhaust flows laterally away from inlet 16, the method further comprising optimizing even exhaust flow distribution by decreasing at least one of density 58, 60 and size 70, 72 of perforations of the variable perforation pattern 52, 64 as the diffuser tube 50, 62 extends laterally away from inlet 16, to optimize and achieve even flow distribution of exhaust flowing axially along axial direction 32 to aftertreatment element 18.
In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different configurations, systems, and method steps described herein may be used alone or in combination with other configurations, systems, and method steps. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims.
