Future Diesel emission standards for passenger cars, light and medium duty vehicles, require the combination of a more efficient NOx reduction performance along with the opportunity to reduce the complexity and the package requirements to facilitate it.
With the increasing availability of aqueous urea, DEF or AdBlue® at service stations, and improved package opportunities, the urea SCR technical solution has been demonstrated to be very efficient for NOx reduction; however the complexity in injecting and distributing the reductant remains a challenge to the industry. The traditional exhaust system contains Diesel Oxidation Catalysts (DOC), Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR), all require additional heat to facilitate each of their specific functions. With some particular package scenarios the SCR catalyst maybe found after the particulate filter where elaborate light-off strategies need to be deployed to ensure activation under many different driving regimes. In addressing this loss in thermal signature to the SCR, significant technical progress has been made enabling the incorporation of the SCR coating within the DPF structure thereby minimizing the need for enhanced thermal strategies.
The purpose of this paper is to show the level of improvement of the novel compact AdBlue®/DEF injection system disclosed in the SAE 2011-01-1318 paper, which enables the SCR coated filter to be located as close as possible to the DOC thereby capturing all the benefits of the new SCR technology. Improvements have been made from the original innovative compact mixer, regarding mixing performance, NOx reduction potential, and packaging compactness including the AdBlue® injector mount, urea deposit prevention as well as back pressure levels, which were considered a major drawback of the original system. In addition to the system improvements, novel simulation approaches and advanced post-processing tools have been developed in the meshing process and the extended use of improved numerical fine tuning.