Method of evaluating a soot quantity accumulated in a selective catalytic reduction washcoated particulate filter (sdpf)

A method of evaluating a soot quantity accumulated in a Selective Catalytic Reduction wash-coated particulate filter of an internal combustion engine having an exhaust gas aftertreatment system including a urea injector, the method comprising:

• determining an urea quantity value to be injected by the urea injector;
• determining a NOx quantity value at an inlet of the selective catalytic reduction wash-coated particulate filter;
• determining a temperature value at the inlet of the selective catalytic reduction wash-coated particulate filter;
• determining a mass flow value of an exhaust gas in the aftertreatment system;
• computing a correction value of a soot quantity using a map correlating the urea quantity value, the NOx quantity value, the temperature value and the mass flow value;
• and
• correcting an estimated value of the soot quantity using the correction value in order to obtain an evaluated value of the soot quantity.

An apparatus for evaluating a soot quantity accumulated in a selective catalytic reduction wash-coated particulate filter of an internal combustion engine having an exhaust gas aftertreatment system including a urea injector, wherein the apparatus comprises a electronic control unit for controlling the urea injector and configured to:

• determine a urea quantity value to be injected by the urea injector;
• determine a NOx quantity value at an inlet of the selective catalytic reduction wash-coated particulate filter;
• determine a temperature value at the inlet of the selective catalytic reduction wash-coated particulate filter;
• determine a mass flow value of an exhaust gas;
• and
• determine a correction value of the soot quantity using a map correlating the urea quantity value, the NOx quantity value, the temperature value and the exhaust mass flow value,
• correcting an estimated value of the soot quantity using the correction value in order to obtain an evaluated value of the soot quantity.