Method and apparatus for controlling reductant injection into an exhaust gas feedstream of an internal combustion engine

A method for controlling reductant injection into an exhaust aftertreatment system disposed to purify an exhaust gas feedstream from a compression-ignition internal combustion engine, wherein the exhaust aftertreatment system includes an oxidation catalyst disposed upstream of a selective catalytic reduction device (SCR), wherein a NOx sensor is disposed to monitor the exhaust gas feedstream downstream relative to the SCR, and wherein a reductant injection system is disposed to inject reductant into the exhaust gas feedstream downstream relative to the oxidation catalyst and upstream relative to the SCR, the method comprising:

• inducing a dosing perturbation in an initial reductant dosing rate;
• monitoring, via the NOx sensor, the exhaust gas feedstream;
• determining, via a controller, a reductant dosing correction term based upon the monitored exhaust gas feedstream via the NOx sensor;
• determining a final dosing rate for controlling the reductant injection system based upon the initial reductant dosing rate, the dosing perturbation, and the reductant dosing correction term;
• and
• controlling the reductant injection system to inject the reductant based upon the final dosing rate.

An exhaust aftertreatment system and controller disposed to purify an exhaust gas feedstream for an internal combustion engine, comprising:

• a selective catalytic reduction device (SCR) disposed downstream relative to an oxidation catalyst;
• a NOx sensor disposed to monitor the exhaust gas feedstream downstream relative to the SCR;
• a reductant injection system disposed to inject reductant into the exhaust gas feedstream upstream relative to the SCR;
• and
• the controller operatively connected to the reductant injection system and in communication with the NOx sensor and including an instruction set, the instruction set executable to:
• monitor operation of the internal combustion engine,
• determine an initial reductant dosing rate responsive to the engine operation,
• induce a dosing perturbation in the reductant dosing rate,
• monitor, via the NOx sensor, the exhaust gas feedstream,
• determine a reductant dosing correction term based upon the monitored exhaust gas feedstream via the NOx sensor,
• determine a final dosing rate for controlling the reductant injection system based upon the initial reductant dosing rate, the dosing perturbation, and the reductant dosing correction term, and
• control the reductant injection system based upon the final dosing rate.