Browse Publications Technical Papers 2007-01-1244
2007-04-16

Calibration of a LNT-SCR Diesel Aftertreatment System 2007-01-1244

An investigation into the post-LNT NH3 generation and NOx slip over an LNT was completed for the purposes of determining the proper calibration for NOx reduction over a downstream SCR. Experiments were conducted in an engine dynamometer on the DW12 2.2L diesel engine that was calibrated for rich operation.
The catalyst system was evaluated at 325°C for three different engine speed/load points. Engine speeds of 1750, 2000, and 2500 rpm were chosen, resulting in a LNT space velocities of 35,000 - 68,000 hr-1. Increased lean times were tested, which resulted in NOx loadings on the LNT that ranged from 0.10 - 0.50 grams NOx/L catalyst. In addition, varied degrees of richness were tested, corresponding to lambda sensor readings of 0.90, 0.92, and 0.94.
LNT performance was evaluated based on it's ability to provide a stoichiometric ratio of reactants to the SCR for NOx conversion. Gross and net NOx conversion was evaluated for a LNT-SCR system. Optimal NOx conversion for this type of system required a balance between providing sufficient reductant for NH3 generation without poisoning the SCR from HC. System performance was controlled by calibration of NOx loading and degree of richness.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 43% off list price.
Login to see discount.
Special Offer: With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.
X