Aftertreatment System Performance of a Fuel Reformer, LNT and SCR System Meeting EPA 2010 Emissions Standards on a Heavy-Duty Vehicle

Diesel exhaust aftertreatment systems are required for meeting both EPA 2010 and final Tier 4 emission regulations. This paper addresses aftertreatment system performance of a fuel reformer, lean NOx trap (LNT) and selective catalytic reduction (SCR) system designed to meet the EPA 2010 emission standards for an on-highway heavy-duty vehicle. The aftertreatment system consists of a fuel dosing system, mixing elements, fuel reformer, LNT, diesel particulate filter (DPF), and SCR for meeting NOx and particulate emissions. System performance was characterized in an engine dynamometer test cell, using a development, 13L, heavy-duty engine. The catalyst performance was evaluated using degreened catalysts. Test results show that system performance met the EPA 2010 emission standards under a range of test conditions that were reflective of actual vehicle operation. Catalyst performance was characterized under multiple testing conditions including the 13-mode Supplemental Emission Test, heavy-duty Federal Test Protocol and twelve steady state engine-operating conditions. Testing results were confirmed by operating the aftertreatment system on a test vehicle over 7000 miles on various test cycles including highway, city and severe service cycles. LNT regeneration, LNT desulfation and DPF regeneration were demonstrated in these test cycles while maintaining repeatable and consistent aftertreatment temperature control. EPA 2010 emission standards were met having low fuel usages for LNT regeneration ranging between 1.0 and 1.5%.