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Future government emission regulations have lead to the development and implementation of advanced aftertreatment systems to meet stringent emission standards for both on-road and off-road vehicles. These aftertreatment systems require sophisticated control and diagnostic strategies to ensure proper system functionality while minimizing tailpipe NOx and PM emissions across all engine operating conditions. In this paper, an integrated algorithm design approach with controls and diagnostics for an aftertreatment system consisting of a fuel doser, fuel reformer, LNT, DPF, and SCR is discussed.

An LNT + SCR diesel aftertreatment system was developed in order to meet the 2010 US HD EPA on-road, and tier 4 US HD EPA off-road emission standards. This system consists of a fuel reformer (REF), lean NOx trap (LNT), catalyzed diesel particulate filter (DPF), and selective catalytic reduction (SCR) catalyst arranged in series to reduce tailpipe nitrogen oxides (NOx) and particulate matter (PM). This system utilizes a REF to produce hydrogen (H2), carbon monoxide (CO) and heat to regenerate the LNT, desulfate the LNT, and actively regenerate the DPF. The NOx stored on the LNT is reduced by the H2 and CO generated in the REF converting it to nitrogen (N2) and ammonia (NH3). NH3, which is normally an undesired byproduct of LNT regeneration, is stored in the downstream SCR which is utilized to further reduce NOx that passes through the LNT. Engine exhaust PM is filtered and trapped by the DPF reducing the tailpipe PM emissions.