NOx Performance of an LNT+SCR System Designed to Meet EPA 2010 Emissions: Results of Engine Dynamometer Emission Tests

The paper covers the NO_x performance evaluation of an LNT + SCR system designed to meet the 2010 on-highway heavy-duty (HD) US EPA emission standards. The system combines a fuel reformer catalyst (REF), lean NO_x trap (LNT), diesel particulate filter (DPF), and selective catalytic reduction (SCR) in series, to reduce engine-out NO_x and PM. System NO_x reduction performance was verified in an engine dynamometer test cell, using a 2007 7.6L medium-duty engine. System NO_x performance was characterized using fresh LNT and SCR along with hydrothermal aged LNT and fresh SCR. Test results show levels consistent with EPA 2010 limits under various test conditions. Catalysts performance was characterized at eight steady engine-operating conditions (A100, B50, B75, A75, B100, C100, C75, C50, across a 13-mode Supplemental Emission Test (SET), and an on-highway Heavy Duty Federal Test Procedure (HD-FTP). System level NO_x conversion ranged from 84 to 99%, SCR contributing between 8 - 25% of total system NO_x conversion. System fuel consumption ranged from 2.3 to 4.7%.