Advanced Close Coupled SCR Compact Mixer Architecture 2015-01-1020
Future Diesel emission standards for passenger cars, light and medium duty vehicles, require the combination of a more efficient NOx reduction performance, a significant reduction of fuel consumption along with the opportunity to reduce the complexity and the package requirements to facilitate it.
Recent activities on catalytic products allows for the SCR active compounds to move from the ceramic substrate located in the underbody to the DPF substrate already located in a close coupled position to achieve the benefit of the highest temperature. This newly developed SCR-coated DPF has massively improved the potential of NOX reduction. As published in the SAE-2014-0132 “advanced compact mixer: BlueBox”  it is crucial to inject Adblue®/DEF with a very high mixing performance level.
The benefit of using the SCR-coated DPF in combination with a high performance compact mixer has been demonstrated  , however new vehicle platform development increases the challenge for exhaust system packaging constraints. The purpose of this paper is to show different exhaust design architectures incorporating a dedicated compact mixer matching compactness, weight and mixing performance. In more details, depending on the DOC and SCR-coated DPF geometrical arrangement from “Axial” to “U-turn” (180 degree from inlet to outlet)   passing through an “L-shaped” (90 degree) each system requires a specific flow management in order to get high mixing performance and related high NOx reduction potential. High mixing performance is managed using dedicated mixer designs where the cavity behavior is improved using enhanced CFD simulation. The paper will specifically give a focus on the proposed “V-shape” about 135 degree angle between the DOC inlet and the SCR-coated DPF outlet which is appropriate for a transversal engine installation in a medium size compact car. The benefit of the installation of the entire aftertreatment system in close coupled position looking at NOx reduction together with CO2 control will be demonstrated.