Apparatus, system, and method for reducing NOx emissions from an engine system

A method for controlling NOx conversion in a selective catalytic reduction (SCR) system of an exhaust aftertreatment system coupled to an internal combustion engine, comprising:

• determining a duty cycle factor based at least partially on whether the engine will be operating under highway driving conditions, city driving conditions, or a combination of highway and city driving conditions;
• comparing the duty cycle factor to a predetermined duty cycle factor range corresponding to highway driving conditions;
• controlling NOx conversion in the SCR system according to a reference tracking NOx conversion mode if the duty cycle falls within the predetermined duty cycle factor range, wherein controlling NOx conversion in the SCR system according to the reference tracking NOx conversion mode comprises generating a reductant injection command based on a first model;
• and
• controlling NOx conversion in the SCR system according to an optimal NOx conversion mode if the duty cycle does not fall within the predetermined duty cycle factor range, wherein controlling NOx conversion in the SCR system according to the optimal NOx conversion mode comprises generating a reductant injection command based on a second model different than the first model.

An engine system having an internal combustion engine generating an exhaust gas stream, comprising:

• a selective catalytic reduction (SCR) catalyst that reduces NOx emissions in the exhaust gas stream by converting NOx in the exhaust gas stream to other compounds in the presence of a reductant;
• a reductant injector that injects reductant into the exhaust gas stream upstream of the SCR catalyst according to a reductant injection command;
• a controller comprising:
• a duty cycle factor module configured to determine a duty cycle factor of the internal combustion engine, the duty cycle factor representing predicted driving conditions of a vehicle in which the internal combustion engine is housed;
• and
• a NOx conversion mode selection module configured to command NOx conversion in the SCR system according to a first NOx conversion mode if the duty cycle factor is within a duty cycle factor range and according to a second NOx conversion mode if the duty cycle factor is not within the duty cycle factor range;
• wherein according to the first NOx conversion mode, the reductant injection command is generated based on a first model, and according to the second NOx conversion mode, the reductant injection command is generated based on a second model different than the first model.