Abstract: According to one representative embodiment, an apparatus for reducing NOx emissions in an engine exhaust gas stream of an engine system having a selective catalytic reduction (SCR) system with an SCR catalyst positioned downstream of a reductant injector includes a NOx reduction target module and a reductant module. The NOx reduction target module is configured to determine a NOx reduction requirement, which includes an amount of NOx in the exhaust gas stream to be reduced on the SCR catalyst. The reductant module is configured to determine the amount of reductant added to the exhaust gas stream to achieve the NOx reduction requirement. The amount of reductant added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst, at least one reductant-to-ammonia conversion characteristic, and a conversion capability of an AMOX catalyst in exhaust receiving communication with the SCR catalyst.

Abstract: According to one exemplary embodiment, an apparatus is disclosed for estimating an NOx conversion efficiency of an SCR catalyst. The apparatus includes a catalyst degradation module for determining an SCR catalyst degradation factor and a NOx concentration module for determining an SCR catalyst inlet NOx concentration based on an interpretation of at least one NOx detector signal. Additionally, the apparatus includes an NH3 concentration module for determining an SCR catalyst inlet NH3 concentration, a temperature module for determining an SCR catalyst bed temperature of the at least one SCR catalyst, and a space velocity (SV) module for determining an exhaust gas SV for the SCR catalyst. A NOx conversion efficiency module calculates a NOx conversion efficiency value based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NOx concentration, the SCR catalyst inlet NH3 concentration, the exhaust gas SV, and the SCR catalyst bed temperature.

Abstract: According to one exemplary embodiment, an apparatus is disclosed for estimating an NOx conversion efficiency of an SCR catalyst. The apparatus includes a catalyst degradation module for determining an SCR catalyst degradation factor and a NOx concentration module for determining an SCR catalyst inlet NOx concentration based on an interpretation of at least one NOx detector signal. Additionally, the apparatus includes an NH3 concentration module for determining an SCR catalyst inlet NH3 concentration, a temperature module for determining an SCR catalyst bed temperature of the at least one SCR catalyst, and a space velocity (SV) module for determining an exhaust gas SV for the SCR catalyst. A NOx conversion efficiency module calculates a NOx conversion efficiency value based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NOx concentration, the SCR catalyst inlet NH3 concentration, the exhaust gas SV, and the SCR catalyst bed temperature.

Abstract: According to one representative embodiment, an apparatus for reducing NOx emissions in an engine exhaust gas stream of an engine system having a selective catalytic reduction (SCR) system with an SCR catalyst positioned downstream of a reductant injector includes a NOx reduction target module and a reductant module. The NOx reduction target module is configured to determine a NOx reduction requirement, which includes an amount of NOx in the exhaust gas stream to be reduced on the SCR catalyst. The reductant module is configured to determine the amount of reductant added to the exhaust gas stream to achieve the NOx reduction requirement. The amount of reductant added to the exhaust gas stream is a function of at least one ammonia storage characteristic of the SCR catalyst, at least one reductant-to-ammonia conversion characteristic, and a conversion capability of an AMOX catalyst in exhaust receiving communication with the SCR catalyst.