Underflow selective catalytic reduction steady state ammonia slip detection with positive perturbation

摘要

A method for treating exhaust gas from an internal combustion engine including, determining if a steady state condition exist and perturbing a reductant injection corresponding the steady state. Measuring a first and a second NOx values corresponding to the steady state and resulting from the perturbation, and computing a gradient of the NO_x values relative to the steady state respectively. The method also includes comparing the gradient of the second NO_x value with one of the first NO_x value, if the gradient of the first NOx value is within a selected range of the gradient of the second NOx value, identifying poor efficiency operation for the engine and setting an estimated reductant storage at zero. Otherwise if the gradient of the second NOx value exceeds a selected threshold, identifying a reductant slip condition and setting the estimated storage at maximum, if not, making no corrections in estimated storage.