CONTROL SYSTEM FOR MOBILE NOX SCR APPLICATIONS

摘要

A diesel powered vehicle is provided with an SCR system (50, 51, 54, 56, 42) which uses an external reducing reagent to convert Nox emissions in a manner which accounts for the effects of Nox transient emissions of the reducing catalyst. Actual Nox emissions produced by the engine are filtered using a variable Nox time constant in turn correlated to the reductant/Nox storage capacity of the reducing catalyst at its current temperature to account for changes in the SCR system attributed to Nox transient emissions. Catalyst temperature is filtered using a variable catalyst time constant corresponding to current space velocity of the exhaust gas to account for changes in the catalyst temperature attributed to Nox transient emissions. The reductant is metered on the basis of the filtered, corrected Nox concentration applied at a NSR ration based, in turn, on the filtered, corrected reducing catalyst (42) temperature.