NOx adsorber catalyst condition evaluation apparatus and associated methods

A method for evaluating the condition of a NOx adsorber catalyst (NAC) of an internal combustion engine system, comprising:

• regenerating the NOx adsorber catalyst (NAC);
• determining whether lambda values of exhaust gas exiting the NAC are less than 1.0;
• storing lambda values of exhaust gas exiting the NAC only while the lambda values of exhaust gas exiting the NAC are less than 1.0;
• accumulating the total time spent while the lambda values of exhaust gas exiting the NAC were less than 1.0;
• setting a condition of the NAC based on the stored lambda values and the accumulated total timer;
• and
• calculating a modified lambda value for each of the stored lambda values, each modified lambda value comprising a lambda sampling rate multiplied by the difference between one and a respective stored lambda value, wherein the condition of the NAC is set based on a ratio of a summation of the modified lambda values and the accumulated total time.

An exhaust aftertreatment system communicable in exhaust receiving communication with an internal combustion engine, comprising

• a NOx adsorber catalyst (NAC) through which an exhaust gas stream is flowable;
• an oxygen sensor positioned proximate an outlet of the NAC, the oxygen sensor being capable of detecting an amount of oxygen in the exhaust gas exiting the NAC;
• a controller in electronic communication with the oxygen sensor to receive detected oxygen amounts from the oxygen sensor, the controller configured to convert the detected oxygen amounts to lambda values, and wherein the controller comprises:
• a rich condition timing module configured to accumulate the total time during which exhaust gas exiting the NAC has a lambda value less than 1.0 and a NAC regeneration event is occurring on the NAC;
• a NAC outlet lambda module configured to accumulate modified NAC outlet lambda values only when exhaust gas exiting the NAC has lambda values less than 1.0 and a NAC regeneration event is occurring on the NAC, each modified NAC outlet lambda value comprising a lambda value acquisition time internal multiplied by the difference between one and a respective lambda value;
• a NAC condition module configured to set a condition of the NAC by comparing a ratio of the accumulated modified NAC outlet lambda values and the accumulated total time to a predetermined threshold value, wherein the NAC condition module compares the ratio to the predetermined threshold value and sets the condition of the NAC only if the accumulated total time is greater than a threshold time.