Selective catalytic reduction ammonia storage control

An exhaust system for treating exhaust gas emitted by an internal combustion engine, configured to perform a selective catalytic reduction (SCR) of exhaust gas, the exhaust system comprising:

• a controller configured to govern a reductant dosing for the SCR by:
• computing a reductant dosing rate based on a chemical model of the SCR;
• determining a temperature modulation factor based on inlet temperature of exhaust gas input for the SCR and on an inlet NOx concentration in the exhaust gas that is input to the SCR device, wherein the temperature modulation factor is determined by accessing a look-up table based on the inlet temperature and the inlet NOx concentration;
• adjusting the reductant dosing rate by scaling the reductant dosing rate by the temperature modulation factor;
• and
• causing an amount of reductant to be injected into an SCR catalyst according to the adjusted reductant dosing rate.

A computer-implemented method for controlling a selective catalytic reduction (SCR) device of an exhaust system of an internal combustion engine, the method comprising:

• governing a reductant dosing in the SCR device by:
• computing a reductant dosing rate based on a chemical model of the SCR device;
• determining a temperature modulation factor based on an inlet temperature of the SCR device and on an inlet NOx concentration in the exhaust gas that is input to the SCR device, wherein the temperature modulation factor is determined by accessing a look-up table based on the inlet temperature and the inlet NOx concentration;
• adjusting the reductant dosing rate by scaling the reductant dosing rate by the temperature modulation factor;
• and
• causing an amount of reductant to be injected into the SCR device according to the adjusted reductant dosing rate.