System and method to manage SCR catalyst NO₂/NO_Xratio

摘要

Systems and methods are provided for determining and controlling an NO2 to NOx ratio reference target in an exhaust conduit between a first SCR catalyst and a second SCR catalyst. The method includes determining a present NO2 to NOx ratio in the exhaust conduit between the first SCR catalyst and the second SCR catalyst, and providing a reductant doser command in response to a deviation of the present NO2 to NOx ratio from the NO2 to NOx ratio reference target.

主权项

1. A method, comprising:
determining an NO2 to NOx ratio reference target to a first selective catalytic reduction (SCR) catalyst of an aftertreatment system, the aftertreatment system including the first SCR catalyst, a second SCR catalyst upstream of the first SCR catalyst, and a diesel oxidation catalyst (DOC) upstream of the first SCR catalyst and downstream of the second SCR catalyst; determining a present NO2 to NOx ratio to the first SCR catalyst, wherein determining the present NO2 to NOx ratio to the first SCR catalyst includes receiving an input that indicates a deactivation condition of the DOC correlated to a reduced NO2 production capability of the DOC, wherein the input indicating the deactivation condition corresponds to cumulative operational data for the aftertreatment system indicating one of a poisoning condition and an aging condition of the DOC; determining an NO2 to NOx ratio deviation in response to the NO2 to NOx ratio reference target and the present NO2 to NOx ratio, wherein determining the NO2 to NOx ratio deviation includes determining a threshold deviation value indicated by a calibration table based on the deactivation condition; determining a reductant doser command for injection of a reductant amount upstream of the second SCR catalyst in response to the threshold deviation value; and providing the reductant doser command in response to the threshold deviation value.