초록 ▼

A diesel powered vehicle is provided with an SCR system which uses an external reducing reagent to convert NOx emissions in a manner which accounts for the effects of NOx transient emissions on the reducing catalyst. Actual NOx emissions produced by the engine are filtered using a variable NOx time

A diesel powered vehicle is provided with an SCR system which uses an external reducing reagent to convert NOx emissions in a manner which accounts for the effects of NOx transient emissions on 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 ratio based, in turn, on the filtered, corrected reducing catalyst temperature.

대표청구항 ▼

1. A method for reducing NOx emissions produced in mobile internal combustion engine applications by an external reductant supplied to an SCR system having a reducing catalyst comprising the steps of:a) sensing one or more engine operating parameters to predict a concentration of NOx emissions indic

1. A method for reducing NOx emissions produced in mobile internal combustion engine applications by an external reductant supplied to an SCR system having a reducing catalyst comprising the steps of:a) sensing one or more engine operating parameters to predict a concentration of NOx emissions indicative of the actual quantity of NOx emissions produced by the engine; b) when the actual concentration of NOx emissions changes and the temperature of said reducing catalyst is within a set range, varying the actual concentration of NOx emissions by a time constant to produce a calculated concentration of NOx emissions different than the actual concentration of NOx emissions; said time constant determined as a function of the relative time it takes for any given fresh reducing catalyst to store said reductant at any given temperature within said set range and ineffective to change the actual concentration of emissions when the catalyst temperature is above said set range; and, c) metering the external reductant to the reducing catalyst in said SCR system at a rate sufficient to cause the reducing catalyst to reduce said calculated concentration of NOx emissions whereby metering of the reductant accounts for the effects on said SCR system attributed to transient NOx emissions.